A few skills will almost always come in handy
-soldering (YT has that covered)
-3d modeling (if you want to print or order a print from one of the 3d printing companies, if you don't print it'll still come in handy to have an exact 3d design so you know where you're going)
-basic handcrafting skills (measuring, sanding, polishing, filing, drilling etc)
You can work on those while figuring out what exactly you want to do. There's sites that sell ready made electronics (and things like 510 connectors) for
vaping (eg modmaker or stealthvape) like
dna boards or PWM boards etc.