The most relevant point made is about the hopper and tank -- a good gun will usually require HPA and always requires a hi-po hopper.
So...
I'd say look for used equipment.
If you mean to say that you have $350.00 exclusively put aside for just the marker... well, the world is your oyster. There are MANY great choices for that kind of skrilla.
If you need a tank and hopper (don't forget batteries and lube), then you're limited to around $150.00 as stated above:
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