Spring is probably going to be the best bet since you are new to sniping. Here is a list of guns going from cheap/not so good to expensive/amazing:
JG BAR-10: $110
UTG MK96: $160
Tokyo Marui VSR-10: around $200
Tokyo Marui L96: around $280
Maruzen APS2 Sniper: $280
CA M24: about $300
Maruzen MK96: from $325 to $400
The next best would be electric. there are a lot of electrics out there but here are a few:
A&K SR25: $200
G&G and CA M14: $250
KWA SR12: $385
Tokyo Marui M14: $400
and many more...
The last would be gas. This is because, without serious upgrades, gas guns are very inconsistent.
KJW M700: $200
CA M24 (with gas bolt): $350?
Tanaka M-series: $350-$450
Tanaka AICS series: $400-$600
Right Hook Fabrication: $900-$2200 (these are super upgraded, and the best you can get stock)
With all of these guns, you will need to be prepared to do a lot of upgrading. (Sniping isn't one of, if not the, most expensive sports for nothing)
After upgrades, be expecting to pay upwards of $500-$600. The good thins is, is that the upgrades don't all have to be at once.
In my opinion:
I hope this helps!