While I can't suggest a good holster, I can give a few pointers.
Like carbz13 and bigmick said, get a good belt. Even if you don't wear one now, you'll need one. I use to only wear belts for work, but now it's commonplace. Excuse my ignorance, but which version of the XD9 did you get (sub-compact, compact, full sized)? My other question is, what is your build? I'm 6'4" and skinny as a rail, so I have deal with pressing. Pressing is a major concern if you're in an area where carry isn't common place, though it should be a concern in general. In the end, I bought myself a Glock 26 (I know, I think they're ugly as sin, but for relieabity it's hard to beat) because of pressing. Anything larger than sub-compact stood out like a whore in a crowd of nuns.
"But Rogers, you're 6'4", how do your hands fit around a sub-compact?" Poorly, that's how. Until I bought a Pearce grip. It replaces the floorplate and allowing my pinkie on the grip without adding much length. I love the thing and plan on adding them to all my magazines for my Glock (when I can find them).