I'm going to say that I have a bit of everything in my garage and I've come to the following determinations...
1. I don't like any racks that sit directly on the floor. The problem is that garages are dirty and full of critters so if the shelving can start a foot or more off the floor it is helpful.
2. My garage is like 12' tall, and a 6' shelf leaves a lot of wasted space, so going higher would be nice.
3. I have areas where I want to put bikes and the lawnmower, etc. So, there are places where I want the shelves to start about 4' off the floor.
As such, I think that one of the best solutions is the heavy duty wall-mounted brackets with shelves. You can run longer brackets up higher for deeper shelves. We have some 18" ones near the ceiling where we have storage bins 20" deep sitting on them. Great up and out of the way near the ceiling. Then, down lower you can use wire or wooden shelves to hold your day-to-day needs. They offer specialty stuff that can hook on as well to hold the gardening tools if you need it as well.
I didn't do my whole garage this way, as I have some gorilla racks and other racks in there, but I did part of my garage with this stuff later on and REALLY wish I had done my whole garage this way.
DEFINITELY: Google 'Garage Shelving' and look at some of the pictures for ideas of what you may want.