Ideally, a shed would though be first on your list of things to buy to clean up the space. Get the things out of the garage that are for yard work, move a lot of the storage items out there as well.
Looks like you have some room above the garage door, up front for starters. I'd re-organize, start tossing the things in your garage that you have not used in a long time. You can put your bikes in the back of your garage, along the back wall, and pull the one your working on out.
In the back of your shop I'd build shelves out of 2x4's from floor to as high as you can go, get those things in the back of the shop off the floor to start with, going through them as you go.
What are the dimensions of the space, long wide high? It looks like the back wall is the start of another room, and the attic above goes over that, is that correct?
Andrew