oh, honey...
i do *not* want to sound like i'm belittling you, but your cart is definitely before your horse right now. cave diving is a truly wonderful thing, and there are also some weirdos who like deep wrecks for some reason
, but i really don't think you need to factor 'someday' into right now's decisions.
ok, so you're a new diver. that's great & i'm thrilled for you! you want inexpensive but quality gear - check. don't know a whole lot yet & are asking around - check. wondering what will last into tech diving - maybe. but maybe not.
i really think you need some reliable recreational gear & see how it goes. you don't need a backplate & wing unless you want one (that's the 'bp/w' someone mentioned earlier. it's a modular buoyancy control device that you can configure to do everything except take out the garbage). there's nothing wrong with using a bp/w as a rec diver and if you're pretty dern sure that tech's where you're going, i'd go that direction - *but* there's also nothing wrong with a low-bells-and-whistles jacket or back inflate bc, either.
and remember you don't have to have new. see if there are other divers in the area. see what clubs or groups you can hook up with. my preference is a group that's not affiliated with a shop since they won't have a certain gear line they guide you towards for profit reasons, but any group is almost always better than none. find someone doing the type of stuff you're interested in and see if they're willing to mentor you or at least discuss your choices. maybe you're thinking 'but there aren't any wrecks locally', but if there are serious divers, they're practicing skills and diving basically every week in your local area. i bought a lot of my stuff from someone who was moving up himself and upgrading. his old stuff moved me forward, was cheaper than new, and came from someone i trusted. there's also ebay, but i'd stay away until you know more - it's a bit too easy to be taken if you don't know what to ask.
but previous posters are very right. tech diving is horribly expensive, and worse when there are 2 in the family.
canister lights can be more than $1300, drysuits at $1500-2000, drysuit underwear is more expensive than lots of wetsuits, *used* sets of doubles start at about $400, classes $300-600 apiece (and there are 4 class steps to be a cave diver), tech computers $800-1700...the list is endless and makes me nervous.
*but* - you don't need all that yet. maybe you never will - perhaps you'll fall in love with photography and spend stupid bucks on a big camera system but be totally happy with your recreational dive gear. so...look to the future but live in the now.
what does that really mean for you?? ok, my recommendations. grain of salt applies, as always.
1) the above mentioned group of like minded individuals, who dive every week. you go too, dive dive dive, ask questions, have drinks after & ask questions, laugh & learn.
2) scubapro jet fins. ebay is fine, used is great, make sure they have the lightning bolt as part of the logo. spring straps to hold them on are highly recommended.
3) a good-fitting wetsuit. see what thickness and styles local divers are using, because i agree nothing can be more miserable than being constantly cold. you'll avoid diving because of it.
4) brass-and-glass spg with 100psi increments
5) the cheapest snorkle in the universe. don't fall for gimmicks here.
6) a bc of some type. this is another place to avoid gimmicks. don't fall for how comfy it is on land - that don't mean bubkus in the water, and cushy padding means more lead needed to sink it.
7) regs. don't worry about highest end, and yoke is fine. if you do go tech, they can be your deco bottle regs. but *do* consider getting both the same. a cheaper octo is not a great idea, because 7a) you should seriously consider a long hose. there are a million threads on them, but a 5 ft hose would be worth thinking about if you're serious.
there are LOTS of great threads right here on sb about cave, deep, wreck, deco, mix...all kinds of advanced dives. i've invested many many hours on reading them & came away richer for sure, so please thumb through some & see what sounds interesting.