Don't bother with leetcode. I recommend you get the minimal knowledge required and start building the MVP right away. That way you will have the motivation to learn.

1. choose a popular language, and familiarize yourself with the basics so you can at least read simple code

2. choose a web framework (assuming you want to build a web app), and watch/read a tutorial that uses that framework to build a web app

3. start building the MVP and search stackoverflow for everything you want to do