Don’t forget to check out both the great CI user documentation http://ellislab.com/codeigniter/user-guide
And google before posting on here. While we don’t mind helping people on this forum, we do expect them to try it for themselves first. A 10 second google hunt (I don’t know, how about searching for “codeigniter template system”) would have given you many results ready for you to explore!
No worries. Yes, you are correct, using a template system will add overhead, but as you mentioned it has it’s benefits. It all comes down to your requirements. Good luck.