For the Subnet-EVM, transactions are paid for by the native token of the platform. You can define initial balances on your chain by setting its genesis to give whatever addresses you want an initial starting balance.
Only 1 token can be used for the network fee, and this cannot be split between multiple tokens.
To learn more about how to build a Subnet, please visit our FAQ, and check out
docs.avax.network for developer documentation.
Our Subnet channel in our discord can also be found at chat.avax.network.