First, read the FAQ section. It's a lot of material but it'd answer a lot of your questions.
Since I'm feeling nice today, here's some answers:
1) For a decent, used, AEG, expect to pay around $500. For gear and eye protection, I'd say estimate another $600 (boots, goggles, BDU's, vest, etc). You don't really need camo or vests to play airsoft either, just get some good eye protection and boots. Get age verified and you'll see the buy/sell sections where you can get good deals.
2) See above.
3) No, clearsoft is not good. It will leave a bad taste in your mouth.
4) You can't bring in guns from the US by yourself.