I think the last bit of anything electronic I did before making my first functional fatass GC portable was connecting a 1.5v DC lightbulb to 240v AC. I've come quite a ways since then.
The way I learned at first was mainly reading Gman's worklogs and trying to mimic his wiring and part placement. I failed badly, but over the years I got better slowly just by practicing and putting together a process. I found it works better for me to plan things out more, e.g. measuring wiring length and pre-cutting lengths of wire to keep things as un-spaghet as possible, and using cardboard/3D printed analogs of major parts like the trimmed Wii mobo and batteries in the case planning phase to get a better idea of the amount of space I needed and where everything should be. Also I practiced soldering on old scrap electronics until I was confident that I knew the right iron temp to use, and could make a good solder joint reliably.
As for the theory bit, that just came with time, study, and questions. Voltage regulators and what type of wire to use used to confuse me, but I spent a good week asking questions and learning how to read datasheets for the parts to find the info myself. It took a while to learn how to navigate the sea of mostly over my head information to find the important bits I can work with, but it's really handy once you pick it up. After that it became a lot easier, and I developed confidence in my ability to research (which is more important than you think), but I still asked questions in my worklog when I was unsure. Never be afraid to ask questions. You may think they're dumb questions, but it's much better to ask a simple question than to make a simple assumption and create a complex problem. Just be sure to not take everything you're told at face value, especially by newer users eager to prove themselves. You will inevitably be given some bum information or suggestions, and it's good to double check things before trying them. Staff are a reliable source of solid info, but pls dun spam our DMs with questions. We like to help, but it can get a bit much sometimes.
Ultimately how you approach learning this hobby is up to you, everyone processes technical learning differently. My recommendation is to:
- Take it slow, read/watch some soldering tutorials and if you have a basic iron available, practice on scrap electronics and get a feel for how to hold the iron steady and produce solid, well heated joints. Wear saftey glasses if you have them, and don't breathe the fumes!
- Study the basics of DC voltage (Adafruit and Sparkfun have some pretty simple articles to start you off)
- Read through some worklogs (especially Gman's) and take physical notes about case design, wire routing, parts used, tools used, troubles encountered, solutions offered, and questions asked, and use those notes to compile a plan and list of things you may need
- Assess whether you have a sufficient working area. You need some space and airflow to not die of flux fumes (you won't really die, but it's not pleasant)
- Work out how much money you're willing/able to spend BEFORE you take the plunge and buy anything. This hobby is a hell of a money sink if you develop a taste for it. Tools will run you over a $100 USD easy if you don't already have any basics, and parts for the portable itself go way higher. Budgeting is very important.
- Second to last: Don't burn yourself out trying to learn and understand everything at once. Pace yourself, one subject at a time, take a few days/weeks break if you need to. BitBuilt isn't going anywhere, and you'll do yourself no good trying to rush.
- Lastly, if you have the mind and patience for it, some basic PCB design practice won't go astray. There are a few decent free programs and youtube tutorials for it, and you'll learn how to read and navigate datasheets in the process. This is completely optional, and it's definitely the most advanced part of portablising, but I think it's worth a try once you have everything else down.
Best of luck my dude!