That is a decent question ducky, alot of guys and gals getting into this sport love the idea of being a dangerous, cool, and mysterious sniper. I am afraid I cannot give you much advice on that, since I mainly do the exact opposite of that in my matches. You know, screaming while running forward and getting shot.
If (as I take the Getting into airsoft more comment) is true, I would suggest you get a practical mid priced AEG rifle with decent range first. I understand that spring and gas powered Airsoft Sniper Rifles look rad and powerful even though they are generally 80-250 bucks, they will take alot of tech time to get running perfectly and at a field legal levels as well.
So focus on getting a light weight rig with a dependable rifle first. And if I may make suggestions, it would be these.
1. Kneepads - wether playing indoor or outdoor, there are plenty of natures little caltrops out there to fuck up your knee! Wearing a pair may seem constrictive at first, but the padding goes along way to helping you move across the playing field in relative comfort.
2. Water Bladder - This I cannot recommend enough! Plenty of airsofters have taken to the bright sunlit woods in high spirits, and came back dry heaving completely drained. Make sure you get plenty of fluids in you before, during, and after play to keep yourself in peak physical condition.
3. Full Face Protection - I know many people dont like to hear this, but wearing full face is simply the best choice to make when selecting head gear. Mind you this can go many ways, a pair of goggles with a balaclava or shemagh, a full mesh praetorian, even a pair of shooters glasses with a hokkatsu iron face is better than nothing. Remember that this hobby is expensive enough without having to add dental bills to the equation.
4. A good Belt - The first piece of every players kit should be a nice rigid belt. Wether a new 5.11 riggers belt, an old A.L.I.C.E belt from a surplus store, even a nice 2 inch leather belt is a great place to put the most important things you will need on the field.
And that is my advice for now Ducky, keep in my that this is just a guideline from some guy on the internet who has been playing for a while. This game is so popular because we can play it anyway we want, so if you truely want to be a sniper by all means do it! I simply hope you will read this advice and get whatever you need from it.
Thanks for the question, and just keep shooting!