The first question to answer is what type of diving do you want to engage in. Are you going to be a cold water (local Lake MI) diver or a vacation diver who dives infreuently in cold water.
if youre going to be a cold water diver some things to consider. 1- IT IS COLD in our lake. Average temps in July at 90' in the Lake is about 50-55 degrees. If wet- I have about 300 wet dives in the Lake, nothing less than a 7mm will work- and invest in a good 7mm, a lot of people (me included) only dive the Lake dry. Dry suit diving is the "norm" on the lake- and I do recommend consideing dry- but only after about 50 wet dives.
Next is bc or wing. I have both. If you choose a bc you have to decide between back inflated and wrap around. Back inflated is better for buoyancy control and prevents a "squeeze" on the chest. Wrap around or jacket style has a wrap around air cell more like a life preserver- can constrict when compltetely inflated
I am a mask coniseuur, I prefer a 4 window- low profile; low internal volume- purges in 2-3 breaths. Also, the side windows do open up the peripheal field. I dive a dark skirt to avoid glare.
fins are also important- can bethe differnce between working hard or hardly working. For my wet rig, I use SP Sea Wing Gorillas, for my dry rig- I use AquaLung Rockets 2- I like the extended foot pocket.
Also- and perhaps most important- the reg. Do invest in a decent reg- if your going to dive local- buy a cold water rig. Both 1st and 2nd stage. Worth the investment.
A computer is also a great investment.
I would also advise to think about buying SOME equipment used first. There are great deals for equipment out there- just need to know what youre buyinh.
A lot of info- Good Luck building your rig.