I have a good few dozen fighters I can't upgrade because there's such a lack of gold- I've finished all of the story modes, and I get through prize fights fairly quickly. It's a bit discouraging because there's little progress.
I'll be happy to answer here and give several tips.
1st do try to subscribe every monthly at least both the Medici Kickback and Crown Jewels monthly offers.
2nd participate fights in several Prize Fight Events, Daily Events, Medici Kickdown Prize Fights, Parallel Realms and Selling Gold Moves that you're Not using at your fighters.
(especially with not desired stats)
3rd. Please do try to be patient and farm up and collect up the Canopy Gold everyday as much you can.
- If you need to complete Daily Ops - then try to take it with moderately small amount of gold.
as for Daily Backstage Pass Goals, well that you can accommodate by establishing a Daily Budget Income to put it and perform on your current fighter's Skill Tree or leveling up a certain move.
4th final advice. The most difficult part here about saving up gold everyday was the hard challenge on upon buying DIAMOND KEYS that costs around 800k and/or 1,000 Rift Coins.
My strategy of fully enveloping over 4 Diamond fighters was just simple.
- Save Up and collect Budget/sources everyday.
Accommodate up to a Million Gold as much Possible