I have a budget of $150/month that I allocate to Patreon/Kickstarter. If I spend a bit more over a month because there were multiple projects that caught my fancy, I try to spend less the next few months.

I mostly spend money on projects that I believe would have a lower chance of happening without kickstarter. For patreon, I mostly fund comics and webnovels.

Sidenote, I dislike Patreon. They have a great idea but the interface is really awful and it hasn't improved much. I wish someone more worthy had had that idea first because with the network effect, it would be hard for a competitor to get traction.