Is it a DA or rotary and what level of finish/paint correction are you looking to achieve?
As a minimum, I would get a fine and medium pad and a fine and medium compound polish, this will give you four combinations of cutting. Remember always start with a fine pad/polish unless you are completely sure of the paint thickness.
Although this is only covering Scholl Concepts products, I found this a useful read on selecting polish and pad combinations, as well as polishing techniques.
http://www.cardetailingsheffield.co.uk/Scholl%20Concepts%20The%20Physical%20Shine.pdf