Should I learn all skills and then sell?
In all ways no. Don't learn everything like web design, content creation, ads... in one go. Learn one thing good but not perfect. You will learn building. Don't waste 1 year learning how to build the craziest websites. Take a week and afterwards sell that skill. It's not that hard and not that deep. Also doing cold calls for example. You don't need a sellers academy before starting to cold call. You will learn on the way.