General Recommendations

Linens	WHITE. White towels, white sheets, white comforter (or duvet cover). Why? So you can bleach out stains. If you have dark sheets or linens, people who use acne-control products will cause bleach marks (from the benzoyl peroxide) on your linens, ruining them. If you have patterned linens, it's very hard to remove a makeup or ink stain without bleaching the pattern. There's a reason why hotels use white - they bleach out all the stains.
No Pillow Shams	Your comforter set comes with cute pillow shams, right? Don't use them. Most guests will leave them on the bed, and sleep on them, and you'll have to launder them far more often than is recommended by the manufacturer.
Pillows	I recommend providing four pillows on a two-person bed: two firm pillows and two soft pillows. Whether you use fiber-fill or down is completely up to you.
Sheets	Costco sells queen and king-sized sheet sets. Each set comes with four pillow cases. If you buy multiple sets, make certain they are the same color - sometimes they have white and an almost-white/eggshell, and it's hard to tell them apart inside the store.
Towels	Costco sells towels in bulk under their Grandeur Hospitality label. Bath Towels (6) Hand Towels (12) Wash Cloths (24)
Decorative Throw Pillows (bed)	One is enough. I have four, which is three too many. It looks nice in the photos, but guests have no idea what to do with all the pillows, and they feel awkward throwing them on the floor.
Bath Robes	You may choose to provide a robe if your guest will be using a shared bathroom. If the guest has an en-suite bathroom (or if it is an Entire House listing), there is no need to provide a robe.

Specific Product Recommendations

View links to many recommended products (on Pinterest)
(linens, accessories, appliances) for your Airbnb listing.