Need more information, species for a start! The amount of lighting and the type will depend on this. Also, are you planning on using just the lighting to maintain the heat? And keep in mind that a dimmer will only work in a constant environment. Thermostats can help you do this much better and tighter, but need the proper type of heating. In many cases, I'd suggest using an LED light strip for lighting, and acquire a radiant heat panel for your ambient / basking heat. But again, species will make a difference. Let us know what you're working with! And what type of material you're using to make the cage.
Cheers, and welcome to the forum