Is it possible to be a professional gambler playing only online casinos? The answer to that question is yes you can! However any sort of professional gambling should come with some caution that most players end up chasing losses and turn into a real gambler which defeats the purpose of trying to profit.
You need to read up on slots strategies first. If you don't know some of the basics of online gambling you could be spilling unnecessary money and it is important to know a basic slots strategy along with blackjack and video poker strategies. As a short summary if you bet on slots you should ensure you are playing with the max number of coins so you get the maximum jackpot amount when you eventually hit.
More slots tips: progressive jackpots and progressive slots are fun but these will eat your money very fast and most of the time you can't really get bonuses on it either. Also if you play with bonus money, the larger your bet sizes are the higher your variance becomes which results in less wagering and accumulating bonus money faster. On top of this if you do win you are setup for larger jackpot wins.
Casino Bonus Hunting
Also known as bonus whoring, casino bonus hunting means to take advantage of online casino bonuses by any means all for the purpose of coming out on top with a profit. Surprisingly you can accomplish this with many games including blackjack, video poker and even online slots believe it or not. For poker bonus hunting you can see the card hunter. Overall it is highly recommended you only play with a casino bonus. This will allow you to get some form of player edge and this is where you can start to profit from the casino. Take advantage of no deposit bonuses and any deposit match bonus above 50% is money in the bank. Just be sure to always meet the minimum wagering and to wager your bonus 200% or more above the minimum wagering. This means casinos will let you play without any restrictions.
If you are looking for bonus money there are over $40,000 worth of deposit bonuses and over $500 worth of no deposit bonuses. Always play with casino bonuses when gambling online.