I wish I could agree with BobW as much as he did credit my earlier post but I have to disagree on a few points:
1) While I agree with the advise as to a computer which is ready for Nitrox I do not agree with waiting to purchase this item. Since today the sanctioning bodies have gone computer only and many students are not taught the tables a computer is a necessity. Having your own which you are familiar with increases safety margins compared to needing to learn a rental units features before a dive. There are many fine choices on the market and I don’t feel the need to get into particulars other than to advise you to keep in mind your aspirations as a diver and grow into more advanced features instead of needing to replace gear you outgrow.
2) Diving dry suit should not require excessive BCD lift capacity. The BCD is only used for surface buoyancy while the dry suit controls buoyancy during the dive. Avoid overweighting and nearly all standard BCD should be suitable with a AL80 tank.
3) Concerns for Regulators are the environment you will be diving and service. As a Reg Tech I can tell you most modern regs can be tuned to great performance. Environmentally sealed regs designed for cold water use are at the top of the scale having a pre-dive switch can avoid some surface free flow and waste of breathing gas. Having effort of breathing adjustment is nice but again a properly tuned reg will not need it. Overbalanced designs will maintain consistent effort of breathing at all depths.
4) a back inflator style BCD or BP&W which has been properly setup, weighted appropriately and used by a experienced diver will swim in any position. The complaint commonly stated about these BCD is face planting at the surface. This is due to divers experience with jacket style BCD with wrap around buoyancy who become accustomed to overinflating at the surface to get higher out of the water. A BCD’s job is to float a persons head and proper inflation of a back inflator style BCD will do so without a face plant. It is only overinflating that produces the face plant effect.
So my suggested order of purchases are:
Computer
Exposure protection
regulator set
BCD
I consider a wrist computer the best option so you can use it with rental or your own gear. If you should opt for Air Integration the computer will still function without its advance features when using rental regs without it’s transmitter.