I think for most people you can't go wrong with our first series, "Real Contact Stickfighting". RCS is mostly focused on solo training and is mostly presented in a format of breaking down a particular strike, footwork pattern, stick combination, etc and then practicing along with Top Dog. The instructional material is interspersed with fights ("If you see it taught, you see if fought.") and interviews.
Lonely Dog's "Power" DVD" is outstanding for all levels.
The KK material is particularly accessible for people with a background in Muay Thai. Some beginners without a MT background find it not too hard to pick up, and some don't.
For getting started in two-man training I would suggest "Combining Stick & Footwork" featuring, , , ahem , , , me. After this try the KK DVD again and you may find that you are ready.