Hi @Fiona917,
In our Airbnb, I provide ground coffee in individual packets, one for each night the guest is staying, several tea bags (caffeinated and decaffeinated), hot chocolate packets if they have kids, coffee creamer, sugar and other sweetener packets, olive oil, balsamic vinegar, soy sauce, salt & pepper, Italian spices, a filled Brita pitcher in the fridge, individual bottles of water on each bedside table, fresh flowers, a bottle of prosecco or wine (Trader Joe's has good inexpensive options) and usually some chocolates or cookies. I finish it off with a handwritten welcome note.
For toiletries, I have small hotel-style shampoo, conditioner, body lotion, makeup wipes and soaps.
I figure its costs me roughly $25-$30 per stay, but I think well worth it to provide convenience and comfort for our guests. I think it's the details that count!
Good luck with your rental!