I also love The Glasgow Vintage Company on Great Western Road. Not been there in a while but it's always been very affordable. All knitwear £10, Levis for about £15, snazzy jackets etc.
Mack and Rose is in the city centre and is also amazing. Does lots of bespoke embroidered and repurposed pieces too. They have an online shop or you can pop into the studio for a good rummage.