Whatever computer language you choose to master, a few things that you will have to learn are:
- Data Structure
- Design Patterns.
As for the languages, if you are thinking for the next 5 years, then
- Objective C => Swift – for iOS
- C♯ – for Microsoft’s environments
If you look at the hiring trends, the jobs have skyrocketed for Java, Objective C (and Swift) and C#.