Which ethereum token should I use?

I am building a project where a user can set up a challenge with a bounty and other users can take on the challenge and win the reward. I have a ganache instance running here where everything works fine using my fake ETH.

But these challenges are meant to be easy to solve and the reward can be paid to multiple users, per se the first 10 who manage to beat the challenge are rewarded. Thus, there are going to be many transactions, these rewards are meant to be $5 or $10 each so it is unfeasible to pay for gas/transaction fees in every single transaction.

I need to find a L2 token where I can have a lower fee per transaction AND the users can go somewhere else to swap it for USDT or any other coin they like.

I've thought about having a server wallet, so all the funds would be inside this wallet and the users would be accumulating rewards which they could rescue later on, going to a profile page or something. But I really want to avoid that. The ideal scenario is the user connecting the wallet to get paid every time they earn something.

TLDR: Which L2 token can I have a lower fee per transaction AND is it easy to exchange? How to make transactions less than $10 feasible using the mainnet or some l2 network?