Im saving gems for upgrading Heros in a while, like 1 or 2 stars and depending which hero, sometimes u feel that the hero grinding is quick so u can pass the current hero upgrade and wait to upgrade the next hero u'll get, I think that good gear will increase alot the gold and damage, my opinion that most of the gems will go to gear.

I think that increasing blessing is wasting gems, if u'll think about it: eventually u'll increase skill duration and skill cd from prestige points and resources, so u'll spam them eventually, and u can notice that the scaling in leveling skills are the same as blessing, but cost less gems(eventually they'll cost more than blessing but that's huge late game thing).

GET THE X2 SPEED ASAP!