Something for you to consider with your weapon for stealth; If you get a weapon that is consistently accurate and sight in your sights so you're always hitting right on target, you could try using black BB's. They are harder to use since you can't watch your BB's flight and adjust your gun on the fly, you need to actually use your sights. However, even once you start firing, it may take a couple of seconds for people to determine where you are. They'll have an idea for direction, but they wont be able to follow the trail of BB's back to your position, which should help your "stealth" aspect a lot.
Another thing I've noticed myself while playing a stealthy role is I don't use up a lot of ammo because I try to avoid large dug in firefights. I use my mobility to close the range between me and my targets before engaging, which also helps save on BB's. Doing this, I can not only pack light (just a pistol belt for my pistol and 2 spare pistol mags), but 1 300rd High Cap (p90, bring 2-3 mid caps instead if you are using any other weapon) will last me a full game.
With stealth in general Mobility becomes your biggest advantage. Another thing you could practice is when to be stealthy and when to not care as much about the noise you make. This can be tricky as it can give away your position, but it can work to your advantage by increasing your speed and mobility in the field.