A regular drawing tablet like a Bamboo or Intuos (or another comparable tablet by another brand) works just as well as a tablet monitor like a Cintiq (or, again, a comparable tablet by another brand).
No tablet will make you magically amazing. It all depends on your own skill.
(that said, there may come a point where you feel like you need to switch from a regular tablet to a tablet monitor, but personally I'd recommend going with a a regular tablet first and building your digital skills on that. You can invest in a nice monitor tablet further down the line, if you feel the need to. But there are plenty of professionals who use some cheap, off-brand regular tablet and do wonders with it. There's a guy named Frenden who you could take a look at, he reviews tablets of all sorts. Just google "frenden tablet reviews" or something and you should find them easily.)
You can use things like iPads and other, similar tablets. However, I'm not sure what the pressure sensitivity on those happens to be; lower pressure ranges means you won't get as fine shifts between line weights and opacity. Unfortunately I'm not really experienced with iPads and similar devices when it comes to art, so hopefully someone else can give you some answers.
Long story short, you can totally use an iPad for art, but you'll have to do some research to see if it will do what you want it to do.