Advice on power apps

I just passed the Pl-900 and now studying for the PL-100. Taking my time and trying to work in parallel with building apps for my current job. I wanted to know how can I improve on the codes/functions/variables required to build great apps, and strengthen my skills overall.

I come from a marketing and business background, I'm hoping to use it to help identify problems in companies and build my portfolio over time. If anyone can offer any input or resources that helped you aside from the learning path on Micorosft. I don't want to just have a bunch of certs with a weak foundation.