I would buy the things separate.
Definitely get a HPA tank, you can get cheap ones for 40$.
I would get a invert helix thermal mask - 30$
Used halo off pbnation - 40$ or proto gravity hopper - 15$
cheap HPA tank from punisherpb.com or ansgear.com - 40$
+ a marker.
You could get a used marker. for 225$ you could get a nice UL SLG, G3 or mini.
Instead of the normal slg.
Co2 on a SLG will not end well at all.