Congratulations on purchasing a great firearm. I personally fell in love with the ruger p89 the moment I laid eyes on it and held it in my hand a few years back. I finally picked one up with stainless steel slide and rubber hogue grips about a month ago. When I did I also grabed 1,000 rounds of american eagle 115grain copper jacketed round nose bullets. So far I have fired 250 of them along with some reloads from a friend and havnt had a single jam or dud round.
As far as other types of ammo, the great thing about the ruger p89 is it has a reputation for reliably firing just about any ammo that says 9mm on the casing. I wouldn't worry too much about brands or bullet grain weights if I were you. Just buy the cheapest 9mm ammo you can find for target practice and plinking ad you should be fine. Ball ammo is less prone to jamming and copper jacket ammo means you probably won't need to clean it at the range to keep it going, but I would recommend a good solvent that works well on copper fouling if yoyu use it a lot.
You should also get some dedicated self defence ammo if you plan on using it for that pourpose. Its more expensive, but you won't shoot it that much. Try to run at least 200 rounds of it through your gun to ensure reliability though.
For the best info I'm aware of on ammo selection, google "best choices for self defense ammo". It should be the first link. It's a long read, but they have all the info you need as well as some recommendations for SD ammo.
There is also a nifty web sight with pictures that shows you how to field strip the gun for cleaning. I can't renember the link but will post it later if you want. Kinda scary taking your gun apart for the first time, but the ruger p89 makes it easy and requires to tools. I always field strip it for cleaning now. Its much easier, and ensures my gun will last a lifetime.
Happy shooting,
-Greg
