Chatgpt sub is more expensive than just their api. I use their api with shell gpt, it costs me less than 1$ per month with my usage.
Learn linux of course.
Download data dump of stack overflow, wiki, etc. Set up software to search through it, for example "codesearch", maybe there is something better. This guarantees independence from bot infected search results.
That's a setup for a decade, maybe then local LLMs will be smoothed out and reliable enough to use daily.
This stuff absolutely doesn't need to be expensive. I was doing electronics for a long time now. I guess I am at professional level but I never got regular 9-5 job doing electronics, I was always doing odd jobs like repair, design, construction.
I only recently got modern tools for this. For years my books, parts, tools and methods were mostly from 70s/80s that I got from various public dumps. That was 10 years ago though, now these places are closed.
If you need to do something really fast and cheap - draw a pcb with sharpie and use ferric chloride to etch it. Modern oscilloscope is a luxury. Since I was working mainly with audio stuff I had a diy amplifier with a speaker connected to it that I used to listen to waveforms.
A lot of tools can made by hand too. There is a ton of old projects for old atmega microcontrollers. One of the best projects like this was sold as generic chinese made "multipurpose tester" which - last time I checked - was not properly designed when looking at the original. Original would this one - https://www.mikrocontroller.net/articles/AVR_Transistortester But everything necessary for this project is here - https://github.com/svn2github/transistortester/tree/master