itch.io gives you support for a handful of approaches:
- Donations for HTML5 games
- Pay what you want donations before downloading a free game
- Premium games (+ pay what you want tip)
- Optionally paid files: you could have free game then charge a few dollars for a bonus pack
- Reward system: you can offer special limited quantity things for sale. You can even collect a shipping address if you'd like to send someone something
Ads and in app purchases are two big ones that itch.io does not support. It's likely we'll never have direct support for ads, but maybe in app purchases in the future.