First get this propane adapter: http://www.airsoftgear.ca/store/inde...roducts_id=400
That will allow you to charge your mag with propane.
Second depending on what you're using the pistol for get different weights of BB's. If you just want to plink pop cans .20g is fine but if you want a bit more accuracy go .25g, if you want to shoot paper targets then I'd get at minimum .28g BB's but no heavier than .36g since I find they don't penetrate paper or cardboard if they're too heavy even though they have less speed and momentum is retained better.
EDIT: Also, where did you get that? It looks like a "UK spec" airsoft pistol.... judging by the VCRA compliant coloured slide.