Cork would be my preferred choice, although it can get expensive...
As for layout plans, you will want to see what's out there for some design inspiration, before I was able to design my own layouts I spent ALOT of time studying track plan books and plans I found on the internet. Before long I was doing stuff like this:
Basement G scale layout (older plan but you get the idea)
HO Scale Marklin Layout if I had the proper space and $$$. This is my multi-level masterpiece