To get a feel what a rebreather is like, you can probably take a class and rent a Drager Ray or Dolphin. Both are pretty simple designs the Ray is depth limited to about 60ft and the dolphin about 130. These are the most popular RBs in the world and are relatively inexpensive. The azimuth which is considerably more money is a better design but is very new.. Personally I never liked SCR rebreathers which all of the above are, but they can serve as an introduction..
Buoyancy control on SCRs is considerably easier than a CCR rebreather (inspiration, Prism, Cis-lunar ect), but gas efficiency and on/off gassing efficiency is no where near that of a CCR.
On all RBS you must be Nitrox certified to take the class, for CCRs most require an Advanced nitrox or equivalent rating.
The azimuth is supposed to have a CCR upgrade option later this year so it definately worth the look... Right now The Inspiration and Prism(assuming their customer support improves) are probably your best bets, I have heard good things about the Megladon but haven't tried one myself.