There is a lot of territory that can be covered between regular diving and whatever Tech diving is. I say that as no one has a definitive definition of Tech diving. If anything, the term Tech Diving is more marketing now then anything else.
Back in the dark ages the 1980s and early 90s before Mike Menduno coined the term Tech Diving, we were all just divers. Some were recreational divers, some were wreck divers, some were cave divers, and a few were Jersey Divers and we were all trying to figure this stuff out. We learned from each other at the back of the boat or at the waters edge.
If you are still at a stage where you are using a single 80, then go get a 30 cubic foot pony or a larger tank, say a 120, and a NITROX cert. They will let you extend your range a long way without pushing the envelope too hard. Eventually, if you keep going, it will be time for doubles etc. which may/will start you on the road to other gasses and decompression. Just take your time and look for good quality used gear to keep the costs down. In doing this, learn how to take care of your gear, its not hard.
Then go diving, a lot, then take a dive, when you get bored go diving, after a short break go diving. When you are done, get another 30 to 50 dives in. Experience will tell you much more about what you will want to do then any of us will ever tell you. Along the way, find some good buddies and a diving mentor who can show you the ropes. Get some training, by all means go at least through Advanced and rescue, but maybe take a break there and go diving, figure out what you are really interested in before getting a lot of cert cards and realizing that you have a bunch of training dives and not many fun dives.
But, if you buy anything right now, make sure one of the first things is a good well fitting exposure suite, be it a wet suit or a dry suit. If you keep ending up getting cold and uncomfortable, your diving life will be short. The sad fact is that most of the divers reading this board will cycle in and out of active diving in 3 to 5 years, life just gets in the way with work, family, kids, health, etc. But if you get to 10 years, you will most likely be in it for the long haul. At some point you will find that you are not diving, you are diving to do something else. That something else can be photo's cave/wreck exploration, science, or any number of other activities. But if you don't find that something, sooner or later just being in the water and blowing bubbles will not do it anymore and you will cycle out.
As for me, I started diving in 1976, got my open water cert in 1979 and after 31 years am still collecting gear. So, take your time and keep it fun.