Kinda nice having a newbie around lol 
Don't worry though bud, that was me for a long time. We're here for ya if you ever have questions. 
Anywho, honestly, batman beyond had some pretty awesome villains and storylines. But one of my favorites, at least too three, is probably Shriek. One of my favorite episodes after all was "Babel" which featured Shriek. I thought it was great overall.