Studio Extras
If you're setting up on a budget, you should be allocating your limited funds to the supplies that will make the most difference: your paints and brushes. You should also get masking tape (hardware store type is fine), a painting surface and a few inexpensive extras.
If you have room left over for more, all the better. If not, this is my advice on things you don't need right away:
You don't need an easel You'll feel more like an artiste with an easel, but for paintings smaller than about 11 x 14, a regular desk or table works fine. For watercolor, you'll be working on a horizontal surface anyways, and an easel will make things harder. For acrylic, you can work horizontal or vertical, but many beginners find it easier to try flat first.
You don't need a brush holder After spending all that money on brushes, it seems like a good idea to get something to protect them. Brush holders are useful, but when you have only a few brushes, you can store and transport them just as well by rolling them up gently in a piece of cloth and securing with an elastic band. Cutoff pant legs or some other stiff cloth works really well for this if you cut the material a little longer than your brushes to protect the ends. Just please don't leave your brushes in the water jug.
You don't need a special water holder These are neat but not really worth the money at the start - an old jar will work fine. Word to the wise: Don't use anything that looks like a glass or coffee cup - I have accidentally drank the paintwater (or dipped my brush in my coffee) on numerous occasions because I wasn't paying attention.
You don't need a special artist's light While you do need good light to work in to avoid eyestrain, it's not necessary to get a specialized easel light, which can be $100 or more. A standard adjustable desk light will work fine, and two will work better. Many artists aim to replicate natural light for working on their paintings. To me, it makes more sense to replicate the light conditions where your painting will be displayed, unless you're planning to hang your painting outside. Regular indoor light is fine, as long as you aren't getting eyestrain. Whatever light you choose to use, make sure you step back from your painting occasionally, or put it on the wall and look at it without your task light. You may be surprised at how the appearance will change.
You don't need an artist's smock or apron An old button-up shirt or kitchen apron will work fine. I do recommend protecting your clothes, especially with acrylic paint. I have gotten so used to wiping my brush on my apron that I absolutely must wear an apron, or I will definitely just wipe the brush on my clothes when I'm not paying attention.