What are the essential technical skills in CS?
- Good and rock-solid understanding of "language theory" a.k.a Automata Theory.
- Data Structures and Algorithms
- Discrete Mathematics
- C and C++/Java. Yes not any one, but both of these. Very essential.
- Computer Architecture.
- Compiler Design and Implementation.
- Software Engineering.
- Operating Systems
- Distributed Systems
- Data Mining
- Machine Learning
If I were to suggest a single technical meta-skill --- prioritize your ability to validate / evaluate your ideas. This may require understanding relevant technologies in depth, understanding user interfaces and how people spend their time online, building prototypes, learning basic statistics, etc.
Consider watching (again?) The Social Network with an eye on the risks for "idea guys".