You will need lubrication for the clay bar. Mequiars detailing spray is fine for this.

I would also suggest an all purpose cleaner as that can be used for spraying under the arches, cleaning the wheels, cleaning the door checks and generally cleaning interior surfaces. I would suggest a trim gel (unless you have color coded the arches). I am using chemical guys trim gel at the moment and its great stuff. A tyre shine is also a nice thing to have , particularly if you have nice wheels as it really compliments them. Merguiars hot sine or something like that. Also a glass cleaner and thats pretty much the basics.