Canvas or board to do your final painting.
Any canvas will do, you don't have to splash out on the fancy stuff. If you have more than one canvas or board, you can paint a series of two or three.
If you don’t have canvas or board, some sort of thicker paper could work. It needs to be able to hold layers of paint without breaking/dissolving. One place you could find board (if you can’t get to the shops) is on the backs of old frames that you no longer need. I also like to use mounting offcuts from my framers, they hold paint really well.
If you’re using canvas or board, make sure it’s got a layer of gesso on it (canvases are often sold with gesso on them already, you can add your own on top, or not). Don’t have gesso? You can use white paint for now.
Acrylics are great and super easy to work with. If you’re comfortable with oils, you can use them instead. Ideally buy a large range of colours, to make it easier to create your colour scheme. If you don’t have a large range available, you can work wonders with primary colours and lots of white.
House paint is also perfectly good, particularly if you’re not keen to mix your own colours. You can buy test pots to match your colour scheme.
I use Golden Fluid Acrylics, they’re insanely good, but they’re not cheap. I also sometimes mix it with cheaper student paint or house paint to make my pastel colours. As you paint more, you’ll probably tend toward better quality paint, as it’s amazing to work with. But if you’re getting started, anything goes.
I like to buy packs of inexpensive brushes. No need to spend hundreds of dollars on them. Having a range of sizes is helpful. If you have some brushes at home, start with them and build your collection as you go.
Other bits and pieces
A pencil, jar for water, palette (or an old plate), A stack of cheap printer paper or anything similar that you don’t mind using up and messing on.