Find a good gundoc. They will be able to do lots of things to your gun to keep it running in tip top shape.
Where did you go for your first game, you probably could have asked if there was an AV rep on the field (assuming it was organized by one of the teams on the forums).
Next game you go to definitely ask about getting AV'ed. Even if you don't use it it still shows that you did take the time to get AV'ed and people may be more likely to help you.
I'm going to assume you know what kind of range and accuracy to expect after playing your first game and in that case an M16 or DMR variant might be your thing.
Pretty much every gun is a realistic replica of modern rifles. Save for the guns that have plastic bodies but they still are pretty detailed and fairly sturdy.
I don't know of any guns that run on air (save for classic airsoft guns) but I'm going to assume you're meaning gas as in a GBB or NBB (TM Mk.23). It's definitely better to get electric.
If you want quality be prepared to pay for it, you'll probably be looking at the higher end of your budget in that case (at least $450+ for the body only). All guns will be fixable or able to take replacement parts, depending on your mechanical knowledge/skill you may be able to do this work yourself or you may have to go to a gundoc to do it for you. It's probably advised to take something like a TM if you don't plan on doing too many upgrades/keep it stock since people seem to have run those for thousands upon thousands of rounds (stock) and haven't broken yet. It's when you start upgrading that you will start messing with things and make it unreliable. Like with a car if you don't open up the hood you'll keep the reliability it's only when you open the hood to do upgrades that you start messing with the reliability of the car.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE