Ok,
On the budget front buying the cannon is just the start, you need to allow a separate budget for x2 batteries, extra magazines, optics (although not as important) and depending what sort of site you play maybe a tac light.
I would recommend getting a sling early too.
I got ICS guns which are mid range quality guns with good internal parts, will splash the cash on a marui shock recoil eventually When I win on the pools