Buying second hand could save you considerably.
This is assuming that none of the gear has issues.
The most universal/diver friendly set-up would be
to get "stage" rigged bottle and clip it onto front side for dives that demand it's use.
AL30's & AL40's seem to be the more popular of choices.
Keep in mind that both are same diameter and little to no cost difference between them.
On just has 30% more gas, I consider this as a good thing.
If back up gas is good, then more IS better.
Consider a regulator that can be O2 cleaned for pure O2.
This option is important if it is ever is intended for use as a deco tank.
A 5' hose on the second stage is nice as well.
Don't forget MOD marking of tank.
I use Dive Rite Stage marker kit, it has interchangeable #'s for MOD.
For me this was a waste though as it has always had 100% since new.
A good reason to consider intended usage.
Good luck, Dive safe.
Scott's BCD's all have D-Rings, or as least I've never seen any Zeagles without them. Zeagle Scuba was born of needs for Tech Diving.
