Some basics and also some not so basics to help you out.
Change your damn sheets. At the minimum you should change your sheets twice a month, but if you're a germaphobe then do it weekly. Clean sheets not only feel amazing, but they cut down on allergens and dead skin cells that cling to the fabrics that could potentially keep you from being healthy. Wash your bath towels weekly too, and please, have more than one — especially if you frequently have guests.
Know your suit size and shirt size (not small, medium, or large). You should also know and understand the value of a tailored suit.
Whether you have to wear a suit to work or not it's still very important to invest in at least one (or two— blue and black) if you can. Weddings, graduations, fancy parties, funerals, and other events that pop up in life will require you at some point to wear one. Make sure you look and feel sharp by investing in a quality suit with proper tailoring and you won't have to scramble at the 11th hour.
How to sew buttons back onto a shirt or jacket.
At some point a button will fall off of your shirt, jacket, sweater, or whatever other garment. You won't be able to rely on your mom to sew your buttons back on so make sure you know how to do it. Bonus: If and when you have kids, their buttons will fall off too and you'll already know how to fix it for them (or even teach them) in a jiffy!
How to make a budget, and stick to it.
Making a budget is important. Unless you're rich, in which case you can skip this or you already KNOW THIS which is why you're rich. But you should know how much money you have coming in and how much is going out.
Budgets will also help you plan for rainy days when you need extra cash or save for a vacation that you really want to go on. They are super duper important. In today's hyper-connected world there are a bunch of budget apps available that are easy peasy to use and you can download right on your phone. Start by exploring your phone's App Store under the "finance" section to find one that works best for you.