Not long ago, I bought about 15 different little soldering kits on AliExpress for like 1-5 dollars each. Instructions will be in Chinese, but that does force you to learn the more universal symbols in the schematics. Also, you can translate the Chinese with your phone. Anyway, after doing those and a bigger AM/FM radio kit I got from Amazon, I'm pretty confident in my soldering skills.

Oh and as far as how I learned, mostly trying to fix broken stuff (radios, amplifiers, VCRs etc,) and then making guitar effect pedals. Thats a good way to learn circuits!!

Note, dont try working on a tube amp or CRT right away. They aren't evil scary like people say but you do need to study up before you go poking around zappy bits. Anything else like an old radio or VCR is totally fine if its unplugged.

I did this pedal 10 years ago. Support these guys!! Dont use amazon.

https://store.generalguitargadgets.com/products/mxr%E2%84%A2-phase-90%E2%84%A2-replica-complete-kit

Now i mostly work on old consoles. Need to recap my 2600, and I modded a dreamcast and a ps1. Granted the Dreamcast didnt even need soldering besides replacing the clock battery holder.

Or, get some broken gameboys on eBay and try fixing them!