Rather than focusing on 1 thing or a couple of things, develop skills for learning and exploring. If you aren't good at reading, do more of that. Learn to love it. Having good skills for reading and comprehension are probably the most important skills you can develop and will pay you dividends hand over fist. It may seem trivial, but I think people tend to underestimate the importance of having good reading skills! Hot on the heals of reading is developing strong problem solving skills. They will help you develop crucial critical thinking skills. Root cause analysis - conditioning yourself to immediately strip any problem/subject down to it's component parts - and being familiar enough with a subject to deconstruct it fully. Whenever there is a new subject, or especially with technology or a new thing to learn I hang out in support forums and try to answer other people's questions about said technology/subject. I have found no faster way to develop expertise in something than forcing myself to learn it inside-out than by trying to support others in answering their questions.
If you develop the skills to adapt/learn/grow then whether or not you are good at one thing is irrelevant. You can be good at adapting and rapidly learning new things, which is far more important in the long run.