Oftenly I use my old piles of altcoins for gambling, due to their value drop in recent months. Most of them were supposed to be successful projects, but majority of them turned out to be overhyped and right now their value is decreasing, so I don't regret using them for online gambling.
Even if you are playing with altcoins which value keep decreasing it doesn't mean its worthless token or coin you may convert them into bitcoin or any other valuable coins in any exchanges.So if you are gambling with any coin then it has real value and if you loss it means its still the loss so only play with that coin if you can afford to lose.