hi buddy,
your most practical option would be to get a dive bottle as well as a standard air tank but as money is tight you're probably better off just buying two second hand from the for sale section on here
there is no "best tank" it all comes down to personal preferance, a lot of people like the guerilla air systems but i find the reg too short and they can be expensive in comparison. so you might have to try a few different ones if you really want to find the one that's best for you
hope this helps
Ryan, team domination