Don't over complicate it. But with these basics, you can make virtually any outfit work in your favor.
Pick a shirt, any shirt, but make sure it's long sleeve and button-down. Two collars isn't necessary.
Black pants, not jeans. These aren't your work pants either. You need something that isn't for the office that you can wear on days to quit wearing jeans all of the time.
I can't tell you which black shoes to get. Use your best judgement. But I am not talking about sneakers or dressy shoes. I am talking about of good comfortable shoes that can flex between dressing up and dressing down. It's your in-between shoes.
A good sport coat or jacket will do wonders. It's dressy enough to keep you off the couch but near as formal as a VIP event.
Accessories can be almost anything. A scarf or muffler will keep you warm without all the bulk of a coat and hat. It's similar to a vest in that respect.
On the plus side of things, consider updating your underwear. A good pair of both cotton and synthetic socks can keep your feet comfortable and cool/warm. I would almost say that sunglasses are a must. It's a close 6th on the list. When you buy a bag, plan on buying at least two, maybe three. You want them to be practical and look good, not be a catch-all and so large that you look like a hobo. Time pieces are jewelry guys. You'll need one for work and for play. Don't use the same watch for every day, it's a bad move.