plastic shelving units down the sides
Lots of translucent crates, so you can see what's in them, and they can be stacked. The lids will keep future dirt out.
You can put screws and nails in small plastic pots (preferably sorted by size) with a squirt of WD40 and shake them.
A large bin so you can throw stuff straight in.
Anything you want to keep, wipe clean (if very dusty, have a bucket of warm water and WUL, and allow to dry, but generally wipe things with WD40 on a rag to reduce future rust.
Do an initial sort into your plastic crates, e.g. garden stuff, carwash stuff, decorating stuff.
Subsequently, you can look at each crate individually, and you will see that in the garden small tools crate, you have seven trowels, most of them bent, broken or rusty, and you can keep one and bin the others. You will also find that your have four bottles of weedkiller or screenwash, or three sets of spanners, and with all your spanners in one crate, you can wipe them clean and put them in sets.
A lot of stuff can be offered on freegle. I gave away several lawnmowers in the last year, and two cans of motor oil for vehicles I no longer have.
What nobody wants can go to the tip.