Every day, you get 20 or more, on 3, 7, 14, and 30 days, you get bonus coins.
Day 3 is 100 coins plus RNG bonus.
Day 7 is 200 coins plus RNG bonus.
Day 14 is 800 coins plus RNG bonus.
Day 30 is 2000 coins plus RNG bonus.
So in any given 30 spin-period, you get a total of 3700 minimum.
I have gotten some 20 coin days and I have gotten the special chests to have close to the base minimum, but at the current price of coinshop games, if you wait a couple of months, you will definitely have enough for a decent game.
If you buy from the daily deal, you also get a few extra bonus coins ($1 = 10 coins), though this is fairly minimal, the bulk of the coinage comes from the bonus chests at 14 and 30 days of coin spins.
I sat on my coins for about 4 months before I bought my first game from the coin shop. Now it seems that I spend it as soon as I have enough for something that looks good…