Yield Yak is one of the largest autocompounders on the avalanche network. Currently they support several strategies for Elk farms. Each of these farms is able to take advantage of Impermanent Loss.
Once you have the proper network you will need native AVAX in your wallet to transact. Treat AVAX the way you would treat AVAX on Ethereum. This is what pays the (almost non-existent) gas fees.