First off I suggest you try shooting from a bench resting the gun and your hands on a set of bags, 2x4's etc just to get things sighted in. I do this with ALL my handguns before heading over to the pistol range. Most NEW C9's have heavy triggers and it takes a couple hundred rounds before it will smooth up and get a wee bit lighter, and by this time you will be used to the trigger.
One problem new shoots have with heavy triggers is they tend to yank the trigger instead of giving it a smooth, steady pull. The yanking action will almost always cause your shots to hit low. This yanking action is not obivious to the shooter, but an expierenced shooter watching you should be able to detect the trigger yank right away. A former co-worker was having the exact same problem with his C9, all his shots would be all over the lower half of the standard silhouette target. This was AFTER I sighted the pistol in to hit dead on at 15 yards. Once we corrected his trigger yanking problem he actually started to hit COM consistantly with each round.
If the sights are the problem, most C9's do need sight adjustments when NIB, then follow the instructions below. The C9 does have adjustable rear sights, can be adjusted for elevation (up/down) and windage (right/left).
Move rear sight the same direction you want the bullet to move on the target.
Hits are low... Move rear sight UP
Hits are high... Move rear sight DOWN
Hits to left... Move rear sight right
Hit to right... Move rear sight left
Once your C9 gets broken in, 200-500rds, it should have no problems feed Winchester White Box 115gr FMJ's. This is probably the most popular range ammo with C9 owners. Another decent brand is Remington UMC 115gr FMJ and JHP's, both can be purchased at Wal Mart for a little more than the WWB's in boxes of 100rds or 50rds.
Hope this helps.
rimfirehunter