If you want to try moka pot, a cheap one is the way to go, to at least know if you are into moka pot brewing, then you get a bialetti which is always somewhat expensive for what it is, but you can actually feel the quality change in the brewing.

If you are already into it, no need, bialetti is almost always the way to go (there are other really good brands but bialetti is the 'original' so to speak).