Not much. I have about 200 bucks in medium size oxy and acetylene bottles. Not bad and they keep me from going to the local welding house too often. The large bottles are big and unwieldy. Your setup should work with the larger bottles.
Those would probably be ok for short practice sessions. Check Craigslist for used bottles. When you take them in to get filled they will give you different bottles anyway. I have the bottles that are around 5ft tall. I have filled my bottles 3 times during my project.
Grant
Check with the welding supply or gas distributor BEFORE you buy used bottles.Most suppliers will NOT fill bottles over certain size if they are not purchased or leased from them.
These bottles are coded with production dates and mfg info.Lots of bottles out there for cheap but you can't get them filled.
If you are planning on doing a lot of gas welding I suggest getting bottles that will last a while.
Bottles about 3-4ft tall will last and are relatively cheap to buy and fill.Spares are always good!
Bill