Most Gunpla do not require painting. I only paint to replace solid color stickers or just add detail. If you are fine with having stickers, then no paint is needed.
As for Gundam markers, they are paint markers intended for doing touch ups. I use them when fixing trimmed areas on the part itself. Sometimes when clipping parts of the runner, you will get a slight discoloration from the plastic being cut. I sue the markers to touch this up. They are also quite runny so exercise caution when using them. I usually use Mr.Hobby mixing trays and drip some in the tray, then either blush it on with a paint brush or use a tooth pick to apply the paint.
There are also ink based Gundam markers which are either for lining or adding weathering or smudging. I use the Real Touch markers to adding weathering to the bottom of each models foot. I like the worn look they give off.
I don't do prime as I don't use Amazon that often. Anyway I have a google Payday soon :) So I'll see what goodies I can get.
Ok I want a HG or MG. So all I need to buy is an HG or MG that says no paint is required(I hate to do that) and also gundam markers? Which colors? The whole pack or just black if it says no paint is required?