I've been on a similar mission over the last few years. Youtube channels mentioned like 3Blue1Brown are great for deeper understanding of a topic, channels like Numberphile and Mathologer are great for getting excited about the fun and beauty of math. I bought a bunch of texts looking for the right place to start but ultimately what's worked for me is enrolling in virtual/online classes at my local community college. It's cheap, it's fun, and it's giving me the external motivation and community I've needed to make progress.