How do I make mobile wooden shelves to display my garden pots?

I want the shelves to be like ladder steps, not directly on top of each other. Also i do not want them to be attached to any walls, so they are completely movable.

I wish I knew this one!

You are going to have to use something like a ladder to get your support. I can imagine something really wild, like an angled shelf unit with the shelves you want, but on small roller wheels at the bottom and attached to a sliding roller mechanism at the top, that attached to a wall. That reduces your flexibility in movement, but it will go laterally along the wall, much like the old library ladders, if you are that old and can remember seeing such, maybe also having seen them on tv in old movies.
Since you don't want it attached to any wall, you have to have at least an upright support also on wheels if you want complete freedom to move the contraption wherever you like, but a word of warning--if the upright is vertical, make the angle of the shelf portion pretty deep, or you will get tip over. Also, if you plan to move it on carpeting you will want bigger roller wheels. By roller wheels I mean those that look like balls with a metal bracing through the middle, and they swivel just like those you would see on rolling chairs for your dining nook. They can be purchased through www.rockler.com or at home improvement stores.

Why not just use a small stepladder?