I use disposable pads and I order them from here and love them.
Washable Puppy Pads Washable Puppy Pads - PersonallyPaws
I have both the regular and plush. I think the regular are better than the plush. The plush do not seem as absorbant to me.
I have assorted sizes but mostly 18x24 because they fit in my pee pad holders that i bought from Pet Smart. I really like the pee pad holders because it helps the pee pad stay put. I also bought medium sized crated for the pups to stay in when i'm not home and the holder is a perfect size for the crates i have. My pups used to toss the pad all over the place until I put them in the holders.
Premium Pad Training Tray - New Puppy Center - Dog - PetSmart