This is some very good feedback. I hope the devs are paying attention to what you and other new players are saying about how the early game feels.
As for what you can spend money on, here is a quote from an unofficial new players’ guide:
Dragon Armor
Your hero can purchase armor using gems. You should save 500 gems and buy Dragon Armor as your first piece. It grants 100% gold bonus, 50% souls bonus, and 50% xp bonus. Gems of War is a completely free to play game. Players who spend real money should consider buying the Death Knight Armor. It’s the best purchase granting a 100% bonus to gold, souls and xp.
The above text was taken from this guide for new players, which was announced in this thread on the official forums.