if you have an ill-fitting wetsuit, you have an ill-fitting wetsuit. If you have a low quality wetsuit, you have a low quality wetsuit. Good neoprene doesn't permanently stretch significantly and certainly shouldn't on the dive. If you are regularly diving where you think you'd benefit from a drysuit, just get one first off. They aren't rocket science, you don't "need" a class to dive one, just some common sense and preferably a buddy who can tell you some of the weird nuances with them, and they're expensive but worth it if you're regularly diving in water below 70F, or diving when it is windy, or doing lots of repetitive dives, etc etc. Not so worth it if you're regularly diving in hot and humid air as it will be a damp suit before you get in it though