I personally started off with O/A in highschool. From there, I purchased a used Miller Thunderbolt Stick welder and started welding together things. One day a farmer needed an axle housing on a tractor welded. I tried welding it for him, and it turned out like ****. From there, I spent about a year with that same farmer learning how to weld/doing welding jobs for the farmer with my stick welder, little did I know he was a welder for the U.S. Army back in the day. I got pretty darn good at it, and moved on to MIG. I purchased a used Lincoln MIG machine and started welding things together with it. I was self taught at MIG, and I landed a job at a local factory welding injection die holders together. I got some of the best lessons I could've gotten from the old timers in that factory on MIG and stick welding.
I then moved on to a die maintenance technician. It required me to know/learn TIG. Which I had never done in my life. One lesson with a 27 year veteran changed that for me. I spent about 3 hours welding. Everytime I messed up, he showed me. If I had something wrong with my technique, he helped me correct it. I even learned how to set up a machine from this guy. He also taught me aluminum welding, which is part of my job now. All the aluminum cylinder heads these days have made repairs a lot easier.
Well, without making it too long, my personal experience and opinion is start from scratch. Learn the basics, and listen to the experienced people that try and help you. Nothing beats hands on experience, and you will only get better with time.