The best unicycle you can get at that price point is either a Club Freestyle from unicycle.com (or one of their authorized resellers) or a Torker LX from numerous sources. This thread discusses the differences between them and also between 20" and 24" wheels.
As you seem interested in getting the unicycle for performance I’d recommend the 20" wheel. It is easier to learn on and more maneuverable in small spaces.
You can get a 20" Torker LX on eBay for $115 to $120 with free shipping.
The 20" Club Freestyle is $125 at unicycle.com but they seem to be completely out of stock at the moment.
Check craigslist in your area. There are many second hand unicycles available from people that tried unicycling and gave it up.