No one said you have to join anything but the best approach and YES cheapest can be joining a club.
1. you are almost guaranteed not to crash your airplane while training with a qualified instructor (which is free at most clubs)
2. If you ever do crash and injure someone or cause property damage your liability insurance will take care of it and you wont be in debt the rest of your life.
3. club members often sell their airplanes, especially trainers, very cheap or even give them away. (I gave a brand new trainer to a kid down the road recently, another guy I fly with gave a ready to fly trainer away last week and my club sold 2 used RTF trainers for $50 each)
You can go your own route but you will be missing some great training and the chance to meet a bunch of great new friends.