It is possible to not lose money at the casino (or even come out ahead) on average if you don't play the wrong games and take advantage of promotional deals. See Casino Gambling for Dummies. I don't recommend gambling in general, but if you are going to do it on occasion then it's best to be informed.
If i remember correctly (never gamble, hope I do not confuse the names lol) Black Jack is the only casino game where the bank is in disadvantage bc the dealer has to make a move. There are certain techniques to use this - and if you use them and win, you get thrown out ;)
Depending on the rule set you can have a slight edge in Black Jack by counting cards. Casinos love people who think they can count cards because most of them either can't or will blow their winnings on something else. Though if you are a serious and successful card counter and the casino figures it out they can ask you to leave (casinos are private property).
There are a decent number of games that with proper strategy you can keep your losses to a minimum. Combine that with getting comp'd (casino pays for your room and/or meals) or other promotions (e.g. join our club and get $200 in free money) and you can break even or make a small profit. That said, I hate casinos and would never recommend gambling. Just if you're going to do it anyway you might as well do it right.
I know the author of the book I linked personally which is why I know as much as I do about gambling. He is actually fairly Mustachian. He bikes around town, doesn't buy much consumerism junk, buys things in bulk when they are on sale, etc. He made most his money counting cards in Black Jack. At one point he had been kicked out of every casino in Las Vegas. He also dabbled in various other business ventures, including real estate. I estimate he was FI somewhere around age 40 or so.
Poker you can count cards and will win something like 51% of the time if you do... but of course the house doesn't let you win, they kick you out. if I am not allowed to play to win why would I play?
Pretty sure counting cards doesn't help you in Poker (I think they reshuffle every hand, though it might depend on the variant), it's more about proper strategy. Also, if you play Poker at a table at the casino you are typically playing against other players and not the casino. So the casino doesn't care how much you win (they just take a cut) and won't kick you out unless you are cheating.