The Kraken is a good choice, but if you are willing to spend more money, get age verified and buy a Classic Army or a Tokyo Marui that will totally be worth the money. You could also buy a Kraken or a Jing Gong, upgrade it and you will have a cheaper gun, better than a Tokyo Marui.
A Low caps is a mag that contain 50 rounds or less and don't have a little wheel to turn.
A high cap is a mag that contain 200 rounds or more, rattle when running and has a little wheel to turn every 30-50 bb you shot.
The best in my opinion are mid caps, they generally contains around 100 bb, don't rattle and don't have a little wheel to turn.