you wont need a ghille in regular open play, you wont have time for it to come in handy.
A sight wont really be useful unless you marker is really consistant. If you choose to get a sight I would reccomend an occuled (spelling) eye red dot sight. It's quicker to sight, and there are no batters to run out.
Shoot the best paint you can afford, this will give you more accuracy (assuming it matches your barrel well) and buy a good barrel. Maybe one that matches the paint you shoot most often. then get sed to the way your 'gun shoots, and you wont need a sight.
-Micah