Considering the time you had under the hood it looks really good. Etching is a good idea. But if I were you, I wouldn't hurry to weld many different materials right away. Stay with carbon steel, change positions, change joint types. You don't even have to weld any joints; practice welding beads on a plate. Just stack dimes and try to be as consistent as you can. Experiment with variables like torch angle, amperage, wire diameter, speed and see what you get. Once you get good at that, that's the skill you can apply to almost any joint.
Then you should maybe try welding SS and apply everything you learned from carbon steel. It's also good to know how to weld pipes. Again, start with carbon. I don't know how much time you spend on the forum, but use it. Ask questions, post more welding photos. Good luck.