First of all, hardware/cold wallets are the most secure wallets. So the best wallets to use with Serum will be Trezor Model T, Ledger Nano X, Trezor One, and Ledger Nano S. However, software wallets like Sollet.io, Ledger, Solong, Phantom, Math, Blocto, Solflare, and Bonfida wallets are also supported by Serum. You'll need an SPL wallet to connect to Serum. Serum (SRM) will continue to add more wallets as they become available.