It all depends on what types of lights, how many watts? and what else you are going to hook up to the genny. I have 6- 500 watt lights and replaced the bulbs with GE Ultra 225w. It has about the same Lumens as a 300w bulb.

Your best bang for the buck for a genny is found at Menards. They carry a 3500w Wen Generator for around $280. It is not too terribly loud and is good on fuel.