I recommend a path toward buying everything you need, especially if you plan to do a lot of dives. It will pay off over time vs. paying to rent stuff every time you dive.
Assuming you can’t afford to just buy it all right away, I recommend you acquire the items in this order as funding allows:
1) Regulator - it’s best not to trust your breathing to a rental regulator that you don’t know how the last 10 or 20 people treated it.
2) Backplate & wing - Especially if you intend to do NE diving, don’t let a shop talk you into an overprices stab jacket BC. Get a nice backplate, $15 worth of webbing, and a decent wing that can be used with both single and double tanks.
3) All the "just in case" accessories for emergencies - SMB, reel, whistle, mirror, light, strobe, maybe even a die marker. These are more important than the computer or any fancy accessories.
4) Tanks - I recommend LP steel, especially for NE or other cold water. If you can’t afford them, get used ones. If you still can’t afford that, get AL80s and an extra 10 lb of lead. Buy at least 2 of the same tank so you can double them up easily later if you want to.
5) Computer - until you buy it, just use tables (it’s good practice to know how to do it for yourself)
6) Dry suit - you’ll really appreciate this on longer dives and in the spring and fall. This can greatly lengthen your dive season (from 5 months to year round in some cases).
7) Anything else you will use regularly (camera, scooter, etc) - only buy if you will use often, otherwise rentals will be cheaper.