I bought a computer as my first major piece of dive gear. It was on sale and non air integrated. The main reason I have it is for helping record dive info and as a bottom timer.
I would buy a reg set...that's my next purchase. I've always rented regs and bc's and wetsuits. I just bought a bp/w setup and my next purchase is reg setup. My reasoning is that im still figuring out which wetsuit to buy.
What's needed for diving?
Regulator, BCD, training, tables,gauges, mask and fins are the major definite haves IMHO
Wetsuit or drysuit for the conditions your diving in both are for comfort and help prevent hypothermia which from what I've read recently can help DCS symptoms to form
Accessories that some divers dive without and others must have with them as personal choice : computer, slate, clips, DPV, etc.
Another thing I didn't notice anyone else point out. Your diving dry which is something I haven't done yet. I assume you use 2 lp hoses connecting to both your suit and BCD. The shops around here usually don't have 2 hoses on the reg setup. So you can set up everything nice and easily.
Add the computer as a maybe later.