I’ve lived here for a bit now so here’s some of my recommendations.
First and foremost, try to buy everyday things outside of NYC if you’ll have the opportunity. It will always be a bit cheaper in stores outside or to the outskirts of places like NYC, LA, or DC. For stuff like clothing there won’t be a difference but for meds and household stuff there will be.
For medications like large bottles of ibuprofen or acetaminophen (paracetamol) make sure you hit up Target or Walmart, not Walgreens, CVS, or Rite-Aid which are all much, much more expensive.
For other medications:
Delsym tablets for coughing
Hydrocortizone cream for bites/rashes/skin reactions
Allergy meds of all kinds if you have allergies
Melatonin of course. Also comes in gummies for both adults and for children.
Check out supplements if you take them. There’s a better variety/quantity in the US.
If you want teeth whitening I would go for something better than Crest strips. You can buy really great kits that come with gels that you put on, which whiten more evenly. I once saw a kit at Target that came with gel and a mouthpiece with a UV light to activate it like you’d see at a dentist.
If you have pets you can get some handy things for them like antibiotic eye ointments that you’d usually need a vet for.
For clothing I really like Vineyard Vines and Madewell. J. Crew is pretty popular with fellow Brits, I seem to encounter at least one every time I go into one of those stores. I like Anthropologie’s US stores better. The Ralph Lauren stores in the US are gorgeous too.
But of course the main thing that you should do is sample all the food! Especially Mexican food. Whatever you do, make sure you get some good Mexican food while you’re there! 😁