90% of markers run on HP, high pressure tanks, Newer markers these days can run on LP low pressure markers, however tehy were designed specifically for angels ( a kind of marker)
a High pressure regulator (HP) will make sure hte air coming out of your 4500 or 3000 PSI bottle is only 850 or so PSI which is more marker friendly.
A Low pressure regulator (HP) will make sure the air coming out of your bottle is only 450 PSI i think... i dont use them buti think its that kind of region...
I owned a Mini as my first marker and i loved it
I went straight for my 68/45 ( 68 cubic inches, thats the size. 4500 PSI thats the pressure it can hold) It was light and held a good amount of air so i wasnt filling to often. I got mine for £80 with 5 years of test left on it Which is an incredible deal
But the market is saturated (in my opinion) with bottles at the moment so you could probably get something around hte same price.
£40 for a heavier smaller tank or £80 for a lighter bigger tank, i thought i would make the jump at hte beginning so i wouldn't have to later...
I hope whichever bottle you get, it allows you to have great fun in paintball