Window treatments - sounds silly but most new constructions don't come with blinds, and many resales take them down to make their home seem more generic to sell better. Doesn't seem important until you realize your whole home is on display to the neighbors at night with the lights on.

Emergency fund is huge. Make sure you have at least $1,000 in cash saved somewhere for all the odds and ends that easily get looked over in home inspections and stuff you'll only find out after living there for a few months.

Home warranty - I personally don't endorse these, but if it isn't worked into the contract and you insist on one, it can run between $500 - $1,500 a year.

Basic tool and yard equipment - Especially if you're coming from an apartment to a single family home: shovels, salt, snowblower, rake, mower, weed wacker, hand tools, buckets, tarps, work gloves, a hose for the exterior of the house, vacuum, trash cans, recycle bin, storage bins

Start up costs for new utilities (installation fees, prepayments for partial months)

Oil - If you have oil heat, you may need to fill your tank if it's not full already, so that can be like $400 - $1,000 depending on size and cost of fuel.

Cleaning supplies - I thoroughly cleaned and disinfected everything (especially the kitchen and appliances and the bathroom) before moving our stuff in. A lot of people buy new toilet seats but I think that's a bit excessive if you disinfect everything anyway.

Gifts for new neighbors - I'm not super social myself, but a lot of people like to bake something for the neighbors and go over and introduce themselves

Landscaping - Good fences and well kept yards make good neighbors. If your yard is in disrepair when you move in, it may make sense to hire a landscaping company to come clean up and mow for the first time to get everything caught up, and take that off your hands while you're worrying about more important things.