You will have plenty of casinos to play slot machines at online, however with the cost of moving money around the internet often being ridiculously high you should carefully consider how you intend to fund your casino account, and also what method you should use for making a withdrawal of any winnings you make too.
The most cost effective way to top up a casino account will be by using a debit card linked up to your bank account as unlike when you use a credit card or a web or e-wallet you will not find any additional fees and charges to be paid for using such a card.
However, one additional thing you should ensure you can do when initially registering as a new player at any casino site is to be able to sign up to a casino site using your own home currency as the one your account will be set at.
Some casino sites may for example only offer their players the ability of funding their accounts using US Dollars, and as such each time you make a deposit using any deposit method those deposits will be subject to currency exchange rate fluctuations and fees and charges too if you do not use US Dollars at home.
So make sure that when you are initially signing up to a casino site you are allowed and able to set your casino account currency in the one you use at home, as that way you will not have to worry about the currency exchange rate for turning your home currency into the one that casino has forced you to use.
But having said that some online slot machine players like to play in a different currency than the one they use at home, as by doing so they will get more playing credits and a much bigger range of staking options when they do so.
Take for example players living in the UK, at the time of compiling this article the exchange rate for one British Pound was 1.29 US Dollars, and as such any player in the UK making a deposit into a casino site using USD instead of GBP would get around 1.29 in credits for every one Pound deposited subject to currency exchange rate fees and charges charged by the deposit method they were using.
So that player would end up getting $129 when depositing £100 and as such would get more playing credits, and that whilst being only a psychological increase in playing credits it is a way of playing some slot players do prefer.
Just keep in mind though you must ensure that you are permitted to sign up, deposit and play using a different currency than the one used in your home country at any casino site you may wish to sign up in a different currency, as some casinos will not permit players to use any other currency than the one they do use at home, however some casino sites will let you sign up in any currency, but always make sure you check!