Rentals are crazy expensive indeed, was lucky to get some early on and try to keep them going. 2200 a day seems like a lot to cover with rewards. I'm between 600-700 and that can be done with ranked battle dec gains alone. So I don't rely much on luck with chests.

That being said it only takes one real good hit with a big dec bag in a chest or gold foil epic/legendary to really get ahead. More chests=more chance of that happening!

What I also do now is rent out all my owned cards (except for lvl 1 commons that are priced at 0.1 dec a day) to off set some of the rental costs. They're mostly useless in diamond anyway at the lower levels. Brings in about 90 dec a day and it grows when I level cards or find new gold/epic/legendaries. Could be helpful for you!