IMO it's extremely un-important to get the Perdix now. You're a brand new diver and who knows if you'll ever even be interested in diving with trimix. Besides, the cost of gear (and helium!) for that kind of diving will make your head swim; updating your computer will be the least of your worries at that point!
Air integration is just a convenience, and not even much of one in most diving situations. It's amazing what the dive gear industry will try to convince new divers to buy. I'm in my 5th year of cave diving and I'm still using my old petrel and SPGs. It's not that much work to look at a SPG. And that's in sidemount, where you have to balance tanks and monitor pressure closely in both tanks. In recreational diving, once you get the hang of it, you might only need to check your pressure a few times throughout the dive.
For a light, a nice inexpensive reliable light is the DGX600. (I bet someone else has already recommended that) They're well made, plenty, plenty bright for recreational diving, and about $70. And they make good back up lights when/if you get into technical diving. I wouldn't spend much more than that.
The wetsuit question is a good one, IMO fit is everything, and of course you need to get the appropriate thickness for your environment. This may take a bit of experimenting. But the bumper-sticker version is, get one that fits you perfectly. New, used, brand, style, etc,...it doesn't really matter. If it fits and is the right thickness for your needs, you'll be happy. If not on either end, you won't. Sorry I can't help you more.
