I bought a hex gridded map designed for PRG miniatures. Each = @6' scale or 1 "person" per hex. Easy to keep track of everything moving. I use waterbased markers to draw on them. I also have RPG "floors" I lay out for hallways, cavern passages, rooms etc.
There's a new system out: 2-sided hex floor plan layout that has everything drawn out in color on heavy cardboard. Street, temples canals etc. Just can't remember the name of it, but they look great.
I think having a special miniature for each player is important: it puts them "into" the RPG environment.
I have unique miniatures for the players @150 total. The players seem to want theirs to be as close to possible as what they envision they look like or carry. I've even gone out & bought several especially for individual players. I then have monster miniatures, usually bought in groups. Each is different and we keep track of them by using: the 1 with the sword/shield/broken sword/wearing the black cap etc. system.
I carry them around in a tackle box with foam inside. (I used to have 2x as many but an EX claimed she bought half so half were hers. No, she doesn't play & doesn't remember what happened to them...)

:curse:
I do my best to find a drawing or picture of what the players are "really" facing so they can imagine fighting that & not a horde of little rats or orcs everytime.
I also have a collection of: trees, brush, hills, rocks, "water," wagons, horses etc that I've picked up over the years. When they escorted a special caravan across country they set themselves up as guards around the wagons & animals, exactly as they would have in "real life." I then ambused them in the "tree covered hills." They enjoyed battling & chasing the bandits in and out of the terrain, plus it gave instant & realistic LOS.