There are some other really great threads on this.
We're short on space in our shop (square footage costs way to much in Hawaii...) and we've gone down a lot of routes.
-we have a 4.5x9ft plywood table made out of an amazon kit with 2 lower shelves. Worked well but also didn't as we'd really need more shelves. For instance we stack 6, 3, 2 and 1mm pvc on top of each other and no one ever wants to pull out the bottom layers and stuff ends up getting stacked somewhere else).
-we've done it vertical but if you stand it on the 4ft end a lot of things end up bowing
We're hoping to get 5x10' tables made out of cut down pallet racks and then we're building custom 4.5x9' shelves on the bottom of them. 4-5 shelves per table using 1" steel tubing. Hoping that way we can split things up a bit more.