Choose the type of gamble you know, the type of gamble you have a passion for, even if you lose it you know you enjoy it. If you want to use a mindset or a strategy for playing, then choose card games like poker. But my favorite of all gambling games was bingo even when I was young, I had fun. I just really love this game. Although we say that winning depends on luck, it still depends on how you mark your card and how attentive you are to Bingo.
Spending your money to a game you enjoy with is like playing for fun and not after money, its a good point for me. If you want to gamble for long period then you have to think of games that you most enjoy and you have knowledge how to maximize your chances to win. Plus you need to set a capital that is not meant for important needs, learn to control and have discipline about the money you will use for gambling.
There's no point in gambling if you're not having fun so it's also one of the factors you need to look for in (online) casinos, find a game that will entertain you so you can enjoy it. There's a lot of games being offered in casinos, you only need to look for a game that suits your taste.
But enjoyment also depends on how well you are doing in the game because even if you really like the game, you'll still get pissed or mad if you keep on losing. So it's not only about the game you choose, but it's also about the situation you have so if you know you're losing, better stop and take a break. Gambling is fun as long as it's not affecting your personal life, so self-control is also a must.