Right now, there isn’t a whole lot of point to your rank within your guild. If you’re any higher than the lowest rank, you can invite people (probably the most important ability), but other than that, you just get the ability to change the announcement, guild symbol, and promote members. Not really anything people are that interested in competing for.
So, what about making some kind of bonus for members of a guild, based upon their guild rank? Not something huge, but a little incentive to actually try for a higher rank.
I was thinking about something like this : At the end of the week, the game could calculate how many resources your guild gained through completing guild tasks for the week, and then give a bonus, depending on your guild rank.
Something like : Rank 1 (lowest rank) = 0%
Rank 2 = 2%
Rank 3 = 4%
Rank 4 = 6%
Rank 5 (Guildmaster) = 8%
This would really help people with collecting some of those resources that are being spread a bit thin (like gems), and also give members a reason to strive for a higher rank.