I agree with you,there is no real point in gambling with Bitcoin because Bitcoin can become a valuable asset in not a so distant future,so it is better to have other coins to play or at least to convert very little part of Bitcoin and play with that money.The cheapest and fastest for me is Litecoin as just some hours ago I deposited about 15 dollars in Litecoin and the fee was 0.01 dollar and confirmation in the next block so it means it is one of the cheapest and best coin to play.
I go even further and use casinos where I can use different FIAT types and I love to play very cheaply that is why I go and choose IDR-Indonesian Rupiah to play even with 0.01 usd to 0.02 usd as a minimum bet by extending my sessions a lot of time thanks to this currency.