As a beginner to machine polishing I've had great success with the HD product line.
Went with 5.5" Buff and Shine pads (Uber and 3D pads are the same) because they have recessed velcro which offers a margin of safety when near protruding objects like mirrors etc.--also makes it easier to center the pad on the backing plate.
I also bought a 3.5" backing plate and 2 of each color 4" pads for the small bits on the car where even a 5.5" was too big.
You might want to consider HD products
HD High Definition Care Care: Detailing Made Simple really user/beginner friendly--long working time, no dust, easy to remove with no oils left behind, won't stain trim/rubber and resonably priced. UNO is very pad/speed dependent so you might be able to get away with just that. Cut with an orange pad, finish with green all with UNO -- depends allot on your paint. You may need HD Polish also if you have softer paint. Or you might only need HD Polish depending on the extent of correction you need and the type of paint.
You'll need a few pads--if you go with UNO I'd suggest 4 orange, 3 green, 2 black and a red to dedicate to each LSPs you plan to use as a minumum. Get a Denture Brush at the Dollar store to clean them on the fly (after each section or two) and Dawn Power Dissolver at Walmart to wash them afterwards. After washing and rinsing well put them between 3 or 4 layers of terry towel and step on them, then let dry overnight velcro side up.
Also, before you start polishing I'd suggest you practice a little--even just put a coat of wax or sealant on the cars just to get a feel for using the HD DA.
You could use UNO to correct with an orange pad, UNO to polish on the green pads (if it needs it) and then use HD Speed (an all in one mild polish/sealant) on the black pads to finish. Then the next morning put on a coat of HD POXY (hybrid sealant/Montan wax) LSP--the look is stunning on dark paint and adds a richness to light colors.