Invest into a course and/or SaaS boilerplate. One course I recommend and have taken is https://www.founderhacker.com. Your background is in design and a lot of things behind design is fundamentally transferrable to tech, the course is guided by practicality which plays into design and I think you may find it valuable.
I recommend a SaaS boilerplate because it aligns entirely with what you've asked which is "powerful, easy to get started and useful career-wise". You're already fluent in html, css and a bit of Python and JS so you're already one step in. You could check out https://www.saasforge.dev since there's a free version you could play around with. From there you could reverse-engineer to learn how it works and was built from scratch.
Good luck!