For which kit to buy, you cant go wrong with anything "pico automotive" branded onto it.
I would strongly recommend (as i believe others here will agree) that the 4423 automotive kit whether standard or advanced it contains pretty much all you need, probe leads, amp clamps (60a and 600a) and secondary pickups to name but a few items in the kit, its a good all round package.
Also its worth looking into the wps500 pressure sensor and accessory kit, i have found it to be very useful in proving lots of faults quickly and accurately.