what dragon naturally speaking software should i buy?

None of them if you're smart. It isn't even close to what you see on TV. I've used them all. Not ONE performs even close and takes months to learn your voice. You spend more time editing the mistakes than you would if you just typed it to begin with. If you just want to play with it, buy it. If you plan on depending on it to accurately type what you say, forget it.

I don't find that software powerful enough to recognise 50% of what you say, that also depends on your speed, tone and accent of course. But overall, there isn't another software that can really match it.