I recently got a 6 oz. popcorn machine for my wife, I've learned a lot in the last month or two about this.
I hear that MegaPop (sometimes called Pop Weaver) is the kind of kernels that you'd like to get.
You probably want to use Flavacol salt, they have a standard and premier option. You can get a quart for about $2.50.
Oil can be tricky. Peanut oil was really good for us and caramel popcorn. I think overall for the price I'd use canola oil. There's a reason taht everyone wants to use coconut oil -- I think it's best overall. However apparently it's really bad for you to use partially hydrogenated oil, you know if you care. =) Problem is, pure coconut oil that I've found from health food stores runs about $9.00 for 13-15 batches of popcorn. Not exactly cheap. Anyhow, I'm rambling.
Check out
www.ht-express.com, that's the site I've found to be the most friendly and informative for my needs. I'm still looking for a local distributor for this kind of thing, shipping can be expensive.
Good luck. =)