@ vanttila The OP mentioned camping/touring in his initial post. I really doubt that he's going to worry about how one more pound affects his speed v. effort if his bike is loaded for touring.

OP, check out this article for some helpful information on lighting and dynohubs, and then this one which has links at the end about weight and friction costs. And if you don't know how to build a wheel, head over to the mechanics section. They can steer you to the right places to start. Or check out your local shop or coop for classes. It's easy, fun and really satisfying to roll out on wheels you built yourself.