My first rain suit was a 1 piece from Nelson Riggs that worked well enough, but it didn't breathe at all and as soon as it stopped raining I would have to take it off. It was about $50.
My best friend had a set of Frogg Toggs. If anybody suggests you should get that, punch them in the mouth immediately. They are 110% useless.
Now, it's Aerostich Roadcrafter or nothing for me. I've already shown how well it works. See the vid I did.
It wasn't cheap at about $900, but you definitely get what you pay for in this particular case.