This is mostly just a tier list, for a guide on how to play arena, go here:
Just some quick tips though. Although this is a tier list, it is imperative that you try to keep a good mana curve (getting all colors). With the new dual color hero weapons, this is less of a problem, but it still does affect tiers accordingly. If a troop has one overlapping color it goes down in value by .5 to 1 tier (dependent on if you have a weapon to cover both your losses that is decent/good in arena) (also, if you have an overlap in the rare department, the ultra rare overlap goes down by a whole tier no matter what weapons you have). If a troop has two overlapping colors it goes down in value by 2 tiers.
Troop placement is also pretty important. Usually (look at troop descriptions in case an otherwise case is stated) you place your hero (the tank) first, your second tankiest minion last (to take hits from last enemy effects), and your highest attack minion second (so long as it doesn’t block one of your troops completely from getting mana… usually this is the biggest issue with common troops.)
Support troops generally require combos, which aren’t the best of to rely on in arena. You generally want damage troops. As such, you should only draft 1 troop max that doesn’t deal damage (1 support troop). Seeing a support troop after you already drafted one decreases its value quite a bit.
Also, when picking your home kingdom, look at two things: does one/two of my STRONG TROOP(s) I have benefit from a mana increase (Rockworm can charge in two turns with a +1 brown, but a +2 brown doesn’t do much else to help.) And do I have overlap (picking kingdoms that give +2 to your overlap are generally pretty good.) Remember it only costs 50 gold to change kingdoms, so its a pretty good idea.
A general rule of thumb is the rarity of mana type usage (not counting hero weapons), although not a science, I find that it maybe pretty close to this, from most to least common: Green, Yellow, Red, Brown, Blue, Purple, so a good purple troop may go up in value because it maybe hard to fill that mana slot.
When Face value is mentioned, this is determined by life + armor + attack x 2. All GoW troops are fairly consistent with this pattern with some slight variations by troop. Life is slightly better than armor in arena though. Face value is pretty important in arena card games, although less important in GoW than some other card games.
As far as just the common category description, remember this is your first pick, so you should go solely on tier lists here (or if you want to try a different troop go for it), but you don’t have to worry about overlap here. Also don’t pick certain cards hoping that you can combo them (cough, scale guard into poison master) because you might not be able to. Go purely based upon value or what you really want to play.
Without further ado, here is the common tier list (troops are in order from best to worst of each tier):
Average face value is between 22-23 and average mana cost is 7.
Rockworm (Br) Face value = 23. 6 damage to the last enemy isn’t that bad, better than the first usually. Create 7 brown gems, if there are enough brown gems on board and/or you got good RNG, you can get extra turns and do it again. Next, this increases the value of other minions that use brown gems on your team. Also, this has 11 life, life is more valuable than armor by a slight amount in arena. A note that this card is a bit risky as it can set up your opponent for 4x or 5x browns. However, the risk is well worth it, as it can solo carry for you the entire game if you get enough brown gems on the board, much more so than goblin (Cost = 8).
Goblin (G) Face value = 23. This card is amazing, fast wind up… deal 6 damage… get an extra turn… most other directed dmg ability commons have 10 life, and this gets 13… amazing value! (Cost = 6).
Pride Hunter (R ) Face value = 23. We love silence… silence drains mana and prevents mana gains for a random amount of time. This also does 5 damage! Only downside is that only the first target can be silenced (Cost = 8).
Satyr (G) Face value = 22. 9 life Is good, ability is similar to goblin with 2 more damage, but the fact that it always hits the last target prevents this from top tier, also slower wind up than goblin (Cost = 9).
Reaver (G) Face value = 23. 5 life is bad, some true dmg troops will 1 shot this… the 3+ red gems to two enemies is an amazing effect however, especially with the 3:1 ratio, you can do 6-7 damage usually, maybe 8. However, using the effect too often will not be as effective on repetitive uses since reds will not replenish by that point, so its not amazing with Goblin Shaman unlike Satyr or Goblin… if only you could combo with Serpent… but a good combo with Banshee and Drake Rider (Cost = 8).
Centaur Scout (Y) Face value = 22. Destroy a row is good since you control this and could line up matches afterwards while gaining the mana effects/dmg of all mana/skulls destroyed. This also deals 5 damage. Yellow is common though… and that 5 damage always hits the first target… fairly fast (cost=7).
Glade Warden (G) Face value = 22. Will not take too many hits with 10 HP, but it has 7 on life which is good. Effect is 5+ green damage, sure it removes its own mana source, but it can remove it from your opponent as well, now this will hit for 8 targeted damage on average first hit! That’s good for a common, and it can do more thanks to a decent 3:1 ratio… even in virtually the worst case it will do 6, not terrible for a fast common. The value goes up if you have a board clear such as a Herdmaster, or something that creates greens such as a goblin shaman (Cost = 7).
Scale Guard (R ) Face value = 22. Very similar to Musketeer except more tanky and does 6 dmg with its ability. Less attack (4), and improves value of minions with poison. If you do get the combo, this could be considered top tier as a 12 damage nuke! Certain weapons and troops can poison, but don’t overly rely on them as they aren’t that great (Cost = 7).
Golem (Br) Face value = 23. Explode a gem is pretty good, also reduces armor from ALL targets if he hits a lot of brown gems… which lets him power up again… also Brown isn’t that common. If your enemies don’t have a lot of armor and as the match goes on the value goes down… the buff made it decently fast for a common that can be charged in two turns with a brown kingdom, but the explosion nerf kind of balances it out. This can deal a LOT of damage with its 1:1 ratio. Do note that the value goes down quite a bit as the battle goes on unless they have a Templar or another armor generating troop, so grab a troop that does damage along with this troop (Cost = 8).
Ghoul (Br) Face value = 23. Only 4 attack, is fairly tanky for a common, it gains 3 attack per use, so it can gain attack fairly quickly, but with its low hp pool, it can get taken out before it gets the chance to use that, but it does charge quickly… destroying 7 random gems is decent at best, on average you get 1 of every mana type and 1 damage with upside for matches afterwards… but you could set up your opponent… This will automatically charge if you run a kingdom with any brown boost, such as Broken Spire, which is a pretty big deal (Cost = 4).
Orc (R ) Face value = 22. Kind of like combining Zombie with Scale Guard. Optimally, you deal 6 damage. You can also gain 4 attack if this troop has taken damage to its life. The problems are that on its own it has 4 attack if not buffed, and like Archon Statue, it likely will be taken out quickly after its life is exposed. The other downside are that you take away skulls (which you could also take away from your opponent) but will prolong the game. The biggest downside is that if there are less than 6 skulls (which if you use this quickly one after the other could happen), you do less than 6 damage and the value goes down. As it stands its worse than Scale Guard due to consistency issues but better than Musketeer (Cost = 7).
Skeleton § Face value = 22. Cool, 5 skulls and a free turn often will give you a free attack with maybe a combo to get some mana… fast wind up… the 4 health kills this card, anything with true damage 1 shots this unless its buffed. If opponent has armor shred, also sucks… only two commons use purple though… pretty slow for a common… Value increases if you got troops or hero weapons that benefit from skulls (Skullblade, Frost Giant, Revenant) (Cost = 9).
Musketeer (R ) Face value = 22. Like Warder, 10 life, damage was nerfed in 1.6 to 5, which is a HUGE issue in arena, even with a fast wind up now, the damage nerf is pretty big (Cost = 6).
Ogre (Blue) Face value = 28. Amazing face value for a common, but bad effect… explode is alright, but its entirely random, which is bad… especially if you hit one of the corners. Those stats though… A MAJOR note is that the ogre can be placed first due to its statpool to protect your hero… and you probably should do this because your hero power is always better than explode a random gem (Cost = 6).
Lance Knight (Blue) Face value = 22. Destroy a row like the Scout, but doesn’t deal damage, instead gives you armor, not as good… also slower than the Scout. Has a 1:1 ratio with greens to give you more armor which is a fine ratio at least (Cost = 9).
Serpent (Blue) Face value = 22. Creating 7 red gems can be nice, if you could combo this with Scale guard, that would be amazing… but you can’t since they are both common… otherwise poison is a bad effect, and this troop is squishy… no damage apart from poison which is too slow and random… it has a few other combos, but its too hard to rely on with your first pick (Cost = 7).
Dire Wolf (G) Face value = 22. Its ability seems pretty good on paper. Deal your hero’s attack (once you get later in its generally 7-8)… maybe a bit less if your hero dies. And this can happen more than once in one cast. Two things pull away from this reality. First, you don’t know how long the debuff will last, and you could lose it before you get ANY value… that’s inconsistent and bad. The second is that the damage is not instantaneous, which sometimes you need to kill a troop before it kills you. Finally, you pretty much only target the front enemy… its best case is too situational to trust in arena… and its worst case is nothing at all! (Cost = 6).
Peasant (Blue) Face value = 21. Destroy 3 gems, and bad face value… however, it instantly charges with one match of water gems… it still is a pretty bad effect to get board control with and the instant wind up should not sway you to pick this card (Cost = 3).
Zombie § Face value = 22. Getting rid of skulls is a bad effect… it does no damage… also increase a random stat by 2 is too random… increasing your magic doesn’t do much on this minion… you heal to full too… but it takes too long for this thing to become a tank… (Cost = 7).
Priestess (Y) Face value = 22. Cleanse isn’t that great… it can be… but not all enemies will run entangles, silence, etc. Give 6 armor is alright, but that’s it… slow for a common too (Cost = 9).
Dwarven Miner (Br) Face value = 22. The effect is awful, sure you get some gold… but destroy a gem… that’s it… instant charge with a brown match, but not enough to justify (cost = 3).
Fortress Gate (Br) Face value = 18. Worst minion in the game… because no attack… it can only tank… but you have your hero to do that… never pick this card… ever… (cost = 9).