Interacting with those protocols will require good amount of $ to be spent, and then again it doesn't guarantee anything. Best suggestion I can give is interact with dapps/protocols where you feel like doing so and leave rest.
Right, specially test net airdrop will ask to deposit in their platform, it can be 30$-50$ even more i have seen a few airdrops but there are no guarantee you will get any rewards it’s definitely depend on your luck i think. So, it’s pretty difficult to predict that which project will pay reward or not. Personally i tried with several project and get only from only a project.