When playing real money casinos, something that you really wanna look for is the casino bonuses. Simply, more or less every casino in the UK has a welcome offer to their new customers which often consists of a deposit bonus and sometimes free spins.
A deposit bonus is something you get when making your first deposit where you get your bonuses matched by a certain percentage, often 100% or in extreme cases 200%. As a comparison, free spins are spins handed out on a slot machine which are 100% real where you have the opportunity to win, just like if you were playing for real money.
However, it is important to notice that all casino bonuses follows with something called wager requirement. That means that you have to play for the money a certain amount of times before you can withdrawal it.