If I had to start from zero with no marketing skills, here is how I would make my first $ online:
1️⃣ Make a free app that solves a simple problem
2️⃣ Promote it on directories
3️⃣ If the app is decent I should get at least a few users
4️⃣ Talk to them, see if they have other problems I can solve
5️⃣ Find one that's easy, offer to solve it for $10 as a feature in your app
Forget about scalability
Forget about making a living from it
The goal is to get familiar with solving problems and get a small win.
Then rinse and repeat with other features/apps, eventually you'll find bigger problems you can solve for more $