I used to gamble with btc a bit but that was a long time ago, when the problem with transaction speed was not around. I think dogecoin is great in gambling, even though it wasn't designed specifically for it. Doge is fast, safe and cheap. As for coins really made for gambling - I find vslice token interesting (not sure whether they loweved the min bet fee yet, though), because it works on smart contract technology (so, scam-free) and I guess it's a pos token, or something, because people who use it get some more as a reward for having some.