A lot depends on where you live and where you ski, but unless you've got solid enough skiing skills to manage ungroomed terrain at a resort, you'll struggle a lot backcountry skiing in a typical situation where AT or telemark gear would be used.
There is an entire range of gear from relatively light XC touring gear to full on Alpine setups that can be used for touring in the backcountry. The trick is to pick the gear that most closely matches your current skills and the terrain you
plan to ski.
Without knowing more about your situation, I'd suggest spending a season focusing on improving your alpine skills and then maybe look into getting an appropriate AT setup. Learning on AT gear is not really a great idea. The release mechanisms aren't anywhere as near as reliable as regular alpine bindings and the gear is built around the idea that it's for relatively expert skiers who don't fall often.
While it may seen cheaper to just get one AT setup, alpine gear is often much cheaper. New AT bindings often twice the cost of basic alpine bindings. It's also much easier to get used alpine gear that is still in good shape. If you decide to stick with it, you can later have AT bindings put on your alpine skis. Or even get a plate that will allow you to switch bindings easily.
This question is almost impossible to answer without a lot more details about where and when you are skiing. It's also very important to get some appropriate Avalanche education if you are venturing into the backcountry.