Yep, the second most important thing to invest in is the education.
Education in its general sense is a form of learning in which the knowledge, skills, and habits of a group of people are transferred from one generation to the next through teaching, training, or research. (http://en.wikipedia.org/wiki/Education).
You should learn something new every day.
If you want higher salary don't you think you should deserve it? And how to deserve it - be more effective for the company you are working for. How to be more effective - learn something new so you can help more or do your job faster.
Believe it or not, the educated people are smarter than the others in the general case. :)
So if you are well educated you will get to know smart people and also these people will know you. So you enter the smart circles.
If you know more things than the other people you can adapt better. So if the times change, you can find another job and survive. :)
"It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change." - Charles Darwin said it.
Did you learn something new today?