Most beginners ask the wrong first question. They ask which skill is "best" — when the skill that works is the one that fits your life: your hours, your equipment, and the kind of work you can imagine doing every day for a year.
Start with your situation. If you enjoy writing, persuasion and social media, digital marketing will feel natural. If you are analytical and patient — the person who asks "how does Google decide?" — SEO rewards exactly that temperament. If you have an eye for how things look, design turns taste into a trade.
Then check the practical side. Do you have a computer, or only a phone? How many hours a week can you honestly protect for learning? A six-week focused course done properly beats a six-month program abandoned in week two.
Whichever you choose, choose one. Depth in a single skill earns; a shallow tour of five skills does not. You can always add a second skill later — most of our students do.