I'm in embedded also, I started this journey at work doing board bring-up. I wrote drivers mostly, not doing any direct electrical work, but after reading the schematics I thought, "oh wow, so that's how they do schematics professionally," followed by "wait, I can do that!" Before that, I just did a few small things with Arduino.

The Youtube channel Phil's Lab has a really good series [1] on PCB design focused on STM32 series chips, that is where I started.

I also got a lot of good information in this thread [2]

And I got feedback on one of my designs on the PrintedCircuitBoard reddit, which is very active and full of amateur and pro-am PCB designers getting feedback. You can post a schematic or layout and people will leave high quality critiques.

For vendors, I have had 2 runs made with JLCPCB (with each run having flaws; some bad, and some not too bad; my board is fairly complex/ambitious so that's part of it). I have heard PCBWay is similarly cheap and good. No quality issues but I've kept traces, spacing, and components on the larger side.

I'm not good at PCB design but am having a blast with it.

[1] https://www.youtube.com/watch?v=aVUqaB0IMh4

[2] https://news.ycombinator.com/item?id=38812244

[3] https://www.reddit.com/r/PrintedCircuitBoard/