1. Check with your university/landlord before you arrive
First things first, find out what furniture you'll actually have in your room. Almost everywhere will have the basic bed, wardrobe, desk and chair, but you might want to buy a bookcase or chest of drawers for extra storage. Bear in mind that you'll have to move any furniture out again at the end of your lease, or even over Christmas holidays depending on your university.
Also check if your landlord is happy with you putting things up on the walls. My uni didn't want anything on the walls at all, but there were already marks on the walls when I moved in so I did it anyway, and just took everything down for inspections. My first landlord also didn't want anything on the walls, but I used white-tac, which leaves less residue than blu-tac, which was fine. My current landlord specifically asked us to use drawing pins rather than blu-tac. He's also been great at letting us hammer picture hooks into the walls and adding shelves!
2. Add individuality with the basics
You can easily spruce up any room just by buying a few of these things - no effort required!
A nice duvet set (with extra cushions and pillows) is a must, as the bed will probably be the most prominent piece of furniture in your room. Make sure you find out what size bed you'll have - in first and second year I had a king-size bed, but now I have a single! - so you can buy the right sized sheets. Duvets and cushions can easily be dragged into living rooms and communal areas to make film nights with your housemates even more comfy.
Most university accommodation (and a lot of rental properties) have horrendous carpets and curtains. While you probably won't be able to replace the flooring, you can easily buy a nice rug to cover it up - these are also essential if you have laminate flooring, which is absolutely freezing in winter! You could also replace the curtains with a pair of your own, as long as you store them safely and replace them when your lease ends.
You probably already have a collection of posters, postcards, photos, and concert tickets. Most hall/dorm rooms will have a large noticeboard above the desk for you to use, you could pin any photos you have onto here. Alternatively, you could hang them on the wall, or on the sides of wardrobes or other furniture.
Plants - or if you're likely to forget to water them, fake flowers - instantly make a room look more homely and inviting. I also love fairy lights, as they give such a warm and cosy glow, but if your landlord has banned these, you could get a lamp with a soft glowing lightbulb.
