Glasgow is the second largest retail city in the UK so you can expect a lot of places to get stuff from. Sauchiehall Street, Buchanan Street and St Enoch area are the main shopping areas within the city centre. Braehead or Forge Retail Park are good too if you do not mind the travelling.
Clothes are sold at very affordable prices at Primark and Madhouse located along Sauchiehall Street. You can find another larger Primark opposite St Enoch Shopping Centre. Branded goods with slashed prices are sold at TK Maxx with outlets along Sauchiehall Street and in St Enoch Shopping Centre.
Sometimes along the street, you will see people selling SNAPfax booklets to students. These are student discount booklets you can use at many places within Glasgow within a year and it only costs about £3. It is definitely recommended. Find out more here.
Great deals also come up at a lot in retail shops during the Christmas and Easter periods.
Furniture
Ikea is the main furniture mall you can get whatever you need to spruce up your room. Woolworths in the city centre (near Glasgow Central Train Station) also offers a great variety of household items.
Alternatively, you can always internet shop at Argos where they offer a multitude of products and you do not even have to step out of your room. Visit them here.