It is practical to teach yourself non-structural welding. If you want to make an end table or a piece of art or a minnow trap or anything where failure of a weld is only annoying, but not dangerous, then go for it. If you want to weld an axle or a roll frame or anything where failure means serious injury or death, don’t teach yourself.
If it helps, my first project is going to weld up a base to turn an old cast iron manhole cover into a coffee table. I know I can’t weld directly to the cast iron but that shouldn’t stop me from making a stand upon which the cover can rest. It should be a pretty good little toe stubber when I’m done. (I hope)