The only best method for topping up an online casino is the one you prefer, the most reliable payment methods for today are Neosurf and cryptocurrencies such as Bitcoin, Litecoin or Ethereum. This said, using a bank transfer is probably not the best one out there as you will have to pay a considerable fee. It’s good for large transfers as the fee is set. If you are okay with paying 3%-4% in fees for a transfer, e-wallets are also a good option.