Ooo, well done, New we have a westie, now a year old. She is a total diva but she rocks my world 
I can only speak for us, and there are real experts on here, but the useful stuff for us is,
Crate- she still sleeps in it at night and she is a year old, with cushions and vet bed to be cosy (nice to have somewhere safe to put her early on)
Bed for naps, we have a small ovis one, it is awesome,
www.orvis.co.uk/p/wraparound-dog-bed/2am5
Brush, comb, hair scissors for cobby bits- we brush her once a day and take her to have her hair cut every 8 weeks or so. Could never get the hang of stripping..with a cut her hair stays very soft.
Dishes for water and food. Metal ones last.
Food- she came from the breeders with Purina, but Millies Wolfheart (Salmon and countryside mix combo) is ace.
Within weeks of having her, she had a skin/ear infection, vet injection/cream cleared it up, we wash her in Malaseb once a fortnight (from the vets), and that and the salmon in her diet seems to keep the skin healthy.
Toys! Westies love 'shake and kill' games, so tough things that squeak, and that can stand a lot of pulling..Kong toys last well.
Pet insurance. You never know. We did this scheme through pets at home for monthly worming drops/tapeworm tablet. It was useful to take her on this regular basis so's the vet nurse could weigh her and check her over- it reassured me. Don't know if I would do it for another year though 
collar, lead, harness, safety harness for the car- We bought a travel crate but she hates it.
Have fun, be patient, kind and gentle. I couldn't be without Hoochydog now 