Lighting is a vast subject, so you really need to know what look or effect you want before you start buying or renting gear. Ideally, you and your DP will work this out and they’ll tell you what they need. If you’re doing everything yourself but you don’t know a lot about lights… well, good luck!
If you’re looking to own your own lights, keep in mind that a typical small lighting kit can run $1,000+. You may be able to get away with DIY lighting solutions from a hardware store, like fluorescent banks and work lights. Even paper lanterns can cast a nice, soft glow for little money. And like the previous poster mentioned, there’s nothing cheaper than sunlight and a bounce card for outdoor scenes. It all depends on what look you’re going for…
JK