Cat Stuff -
Litter and Litter Trays
One litter tray per cat and don't forget you will need a scoop to remove waste products. In order to keep litter dust from spreading, you should consider buying a litter tray with a hood. They should have waste products removed daily and at the same time be topped up with fresh litter. There are hundreds of types of litter product. My advice is simple here, buy the cheapest and if not good enough for whatever reason then buy the next cheapest. Your cat probably couldn't care less and some litter products are priced at stupid prices. Other things to consider are that some litter products put up large amounts of dust and cat litter that clumps easily is better than a brand that doesn't.
The one on the left below is probably better than the one on the right. It will keep dust to a minimum.