These patterns are called tells. A tell is when someone gives away their hand by an involuntary action. Some common tells are the way players arrange their cards, or playing with their chips when they have a good hand, or rubbing their face when they are bluffing In a practice poker room you also get the experience of learning how to watch your money, without losing your shirt when you make a mistake, which will happen at first.
One of the biggest problems with learning to gamble in a casino is that the dealer and the other players are not forgiving. By this I mean let's say you are playing roulette, a first time player may not know that until all winnings are placed on the table you may not take your winnings. Getting a warning from the dealer the first time you play can be embarrassing and unnerving to a new player. So by playing in an online casino at first you will learn the rules, procedures and the etiquette for playing in a land based casino.
If poker is your game it is a little different, most games depend on luck and all you really need to know if the basics, but poker is totally different because you are playing against other layers that know all this information already. When you feel confident enough then go to the casino and find the game you want to play and spend some time watching the other players.
You want to find a table where all the players are less skilled then you. This will give you the edge, but make sure you watch carefully. Many times players will do things to make themselves look worse than they really are to give the other players a false confidence. Then as you see yourself getting better and better you can move up to higher stakes tables and against better players. Once you get confident and see your skills increase so will your bank account.