• The 80/20 method: You can get 80 % proficiency in a subject in about 6 - 12 months.
• The 10,000-hour rule: You can become an expert at something if you spend 10,000 hours of deliberate practice on it. 

To go from zero to 80% (good enough) requires a different approach than that needed to get from 80% - 99% (world-class). The last 20% also requires a different level of commitment. For instance, Stephen King spent 6 - 8 hours daily for ten years before he succeeded as a commercial writer.

The gains disproportionately accrue to people at the top. Stephen King probably sells more books than the rest of his category combined.

Being good at many things probably means that you are at 80% of your potential in all of them. It is not enough to stand out. 

Pick a ...