Skills that you can grow and be trained

1. Analytics - you need to analyze campaigns, landing pages, keywords and bunch of other data to be successful

2. Creativity - you need to be creative to write some interesting content, or be able to judge the work of the designers and creative team

3. Curiosity - you need to test lots of staff and be curoius to learn more staff every day. The industry is changing very fast.

I recommend you also checking out my latest article on 10X marketers. A 10X marketer is an individual who is thought to be as productive as 10 others in his or her field.
https://www.incredo.co/blog/the-world-of-10x-marketers-and-developers

This will help you also to find what skills you need to have that are normally hard to be trained for!