Quick Answer
Pick one platform first: Android (Kotlin) for a broader entry-level market in most regions, iOS (Swift) for higher average pay in the US and UK. Learn the language, learn the modern UI framework (Jetpack Compose or SwiftUI), ship two or three real apps, and get at least one into an app store. That path, done consistently over 6 to 12 months, is what mobile employers actually test for. You can do the whole thing with free resources.
What a mobile developer actually does
Choose your platform first, not both at once
The iOS path: Swift, step by step
The Android path: Kotlin, step by step
Core skills every mobile developer needs
How long does it take with free resources?
The portfolio mobile employers want to see
Where to find mobile developer jobs
Final recommendation
FAQ