Sniper rifles have a very specific niche in airsoft, they do not operate like their real counterparts in giving you that insane range and accuracy out of the box.
Regarding G&G packages, stay away from them. The batteries and chargers they come with are beyond cheap. The chargers themselves will wreck batteries as they don't have a smart shut-off. That being said the G&G combat machine series is probably one of the best selling starter AEGs and for a reason.
All you need is good eyepro, a mesh mask for you mouth, the gun and a smart charger with a couple of batteries and some BBs. That will be fine for skirmishes at walk-on days. If you get into longer games you'll need more gear.