I know that I need a BC, reg, wet / dry suit ect, ect but the real question here is what is necessary to go enjoy a dive and what can wait?
Well, in order to dive, in general you need a mask, a regulator, a BC (some would argue this), a tank, some kind of exposure protection (not always necessary, depending on where you dive) and fins. If you are asking in what order one should purchase these things, you will get a number of answers.
Mine is that the things that have to FIT are things you need to buy early. Exposure protection is very fit-critical. A poorly fitting wetsuit doesn't insulate, and a poorly fitting drysuit may be difficult to vent, or impair mobility significantly. Being cold or uncomfortable will lead to diving less, and diving more is what builds your skill and makes diving more fun.
A BC that doesn't fit is either uncomfortable or even can make diving harder to do, if the BC is too big and sloppy around the diver.
If you have a reasonable source for a rental regulator that is of decent quality and well-maintained (we have quite a few of these in the Seattle area) then a regulator can be put further down the list. Tanks can be put off for a long time, particularly if you live somewhere where diving has to be done as well-planned trips. In a place like where I live, owning one's own tanks makes a spur-of-the-moment evening dive a lot easier to do.
Unless your rental regulator comes with one, you will need a depth gauge/timer. You do not need a computer right away, especially if you are doing relatively shallow local dives. Computers become much more useful if you are doing dive travel, but really only then if your gas consumption is low enough that NDLs are limiting your dives, rather than gas supply. People dove tables for many years!