Which online casino should I use?

There is no single answer to this question really, as there is no single online casino that could be definitively described as the best one to use. It really depends on several factors. If you live in the United States, for example, the best casinos for you will not necessarily be the same as for someone who lives in the United Kingdom. Any personal preferences or specific requirements you have need to be considered too.
The most important thing is to make sure that you use a reputable and trustworthy place to play.