Honestly, the small bonuses you get from using a "gold farming" troop like alchemist are just a drop in the bucket. PVP is the most reliable place to earn gold, and doing "Casual PVP" can be a good place to do that if you want to be more selective about the teams you're facing. You can pay 50 gold to get a new set of three options if the ones you're given look too difficult. That 50 gold is a small price to pay if it gets you an easier win worth 1000 gold or more.
To overcome some of the difficult teams, a reliable approach is to use a looping team where you control the board and never let the AI take a turn. You can find lots of different builds on the forums, but some famous ones are Treant, Alchemist, Valkyrie, Banshee, or Green Seer, Giant Spider, something, something, or Hellcat, Alchemist, something, something (the somethings are whatever works for you - lots of troops can be fed leftover mana from those looping combinations). You just need to watch out for Mab (and other troops that can inflict freeze) when you're using looping teams.