Are you talking about ceramic tiles? You can buy from any building material store, e.g. Home Depot, Rona, etc. The costs depend on the quality and pattern, ranging from $1.00 to $5.00 per square ft. However, since you just need for your bathroom, which is a small area, you can buy a limited quantity (a leftover portion for a large order), which usually gives you a deep discount. The store will show you what kind tools and all supplement materials you need. I did my bathroom wall and floor. I think it is the easiest do-yourself project. Good luck!
Using ceramic tiles wall on the bath room other than around the bath tub is not in fashion these days. Because today’s paint is very water resistant and DIY friendly. The ceramic tiles you choose, other people may not like it. You may not like it after few years. Even tile could be changed or painted on. They are either a big job or do not have best result. So has tiled wall may not help your resell value.
There are drop in tub like the one we saw in hotel. It has tall walls build in. You don’t need to tile wall around the tub any more.