I need an idea about how to make an efficient
I suppose it couldn´t make geometric operations, it would only use glRotate, glTranslate, glScale, glLoadMatrix and glGetIntegerv.
Due to the fact that I need the camera’s matrix for some certain things, I store, calculate and load that myself. I suggest you do the same, or else you may end up rewriting your camera class. Aside from that, there really isn’t much to writing a camera class. For a decent beginner’s eye view of what a camera class should look like, take a look at some of the tutorials available on the net.
Here’s a bone for you www.gametutorials.com.