What I do, according to Niko's guide, is - League x2 of my lvl ( in my case 3lvl = 6$, Cup - 7$, and CL - 8$ ).
So far, I'm getting full attendance, 5% bonus and decent money income.
I've put bonus rewards for each win in each competition ( 20k, 30k and 40k ).
The income I get, is enough to cover all my expenses + buildings and buying new, young players for the future.
I hope this helps you.