Don't get a sniper rifle as a first gun. Regardless of the skill requirements and cost of upgrading them, they are specialized tools for a specialized job. There are a lot of scenarios where hanging back and trying to snipe is counterproductive (rushing an objective, fighting in a building etc). If you still want to try sniping, get a sniper rifle as a 2nd or 3rd gun after trying the game out and learning what you like from experience.
For a first gun, I'd say get an AEG. They're usable in any scenario, and don't require huge investment of time and energy just to get working passably.
Airsoft is where expensive things go to die.