Been there seen and done that.
OK, you need to know your mission and devise your organizing scheme before you look for stuff to organize with.
1. Level of care.
2. Most likely length of transport.
3. What cases do you need to be most prepared for?
From these, determine your supply and equipment items and quantities.
Now, some tips which will affect your storage organization mechanism :
4. Buy items in the same form you would if they were going into a kit (individually packaged, tough pkging, with product name and any outdates readily visible); they will hold up longer against vibration, heat, cold and dirt/dust. Do not buy unitized supplies unles you are sure through experience they are adequate, often they aren't.
5. Consider the scheme of working from your kit(s) and use your storage as primarily resupply for supplies for the kits, or to supplement if things get hairy in the unit.
6. Use the basic rules: stuff you use goes where you can reach and see it, stuff you don't use often a little further out, and stuff you don't use...why keep it?
Do not be afraid of "white space", if you don't stuff every nook with stuff you can find the right stuff better. (Kits help with that too).
OK. NOW think how-to and hardware.
BOOKENDS: velcro on bottom and bottom of those shallow long shelves on the drivwer's side of some units. Use metal bkends not too high or wide.
LG FREEZER ZIPLOCS: use as dust cover, gatherer of pieces or trailoingthingees, and mark any outdates etc on the outside. We use them for an IV start kit, everything for one IV (stuff for two tries and one bag of solution) in one bag. Can see in. Seal it to detect kits having been raided for parts.
KITS: smaller kit bags for stuff like oxygen fittings, small tools kit, flashlights parts (bulbs and batteries, maybe a spare light). Osh hardware sells three piece zippered canvas bag set with belt loops and varying sizes, cheap.
BINS: go to Dollar Tree or something like that to buy them. Use glue-backed velcro (do not buy THAT at $tree) to hook them together, to the bottom of a tray ot shelf, etc.
CLEAR TRASH BAGS: dustcovers etc same as ziplocs.