These two books will get you started, I was very much in the same boat as you and endeavored to improve my mathematical skills in a self directed manner.
"Practical Mathematics", C. I. Palmer (great for practice and learning your stuff in a framework that isn't boring)
"Mathematics for the Nonmathematician", Morris Kline (great for staying inspired, it teaches a lot of history with good exercises)
"Practical Mathematics", C. I. Palmer (great for practice and learning your stuff in a framework that isn't boring)
"Mathematics for the Nonmathematician", Morris Kline (great for staying inspired, it teaches a lot of history with good exercises)
This website also has some great recommendations for books: http://math-blog.com/2007/07/17/ten-must-read-books-about-ma...
Good luck! I've enjoyed math much more since I've tackled it on my own time and under my own desire.