Re the mask as Tom said keep your mask to start..with such a small amount of cash to spend on your setup, i would keep the JT mask you have and spend more on the marker.
Re the 12oz syphon you would need to get a newer bottle some guns CAN run on CO2 but dont like it most modern gun prefer AIR. You would also be looking at getting a hopper I guess the one you have is gravity fed and not electronic/ assisted hopper. A 2nd hand hopper is any where between £20 upwards.I used to play a few years ago so i've got pots, pack etc, its really just the marker i'm looking for. I've still got my phamtom with a 12oz siphon bottle but you boys would piss your pants laughing if i turned up on a site with that.