If you're good at drawing, I think a tablet would be a good idea. But, if you're pretty bad, like me, then I don't think it would be worth it. I use a mouse and Paint.NET, and once you get used to it, you can make great art with it. I have looked at tablets before, but it seems the good quality ones [the only ones I think are worth buying] are expensive.
At the moment, I am learning to draw. When I get good enough, I'll invest in a tablet. I think that is a good order in which to do things