I think we all get in that mood where we absolutely need something.. or maybe it's just me. Anyway if you like to have mini shopping sprees like me then keep on reading. Also, I will list all links below.
1) Asos I didn't hear about Asos until I got to college and that is because I Google "who give student discounts". I would highly recommend them, they have great pieces and always have a sale on top of the 15% student discount. If you aren't a student the prices still aren't that bad.
Even though H&M doesn't have a cool student discount like ASOS, they still carry some pretty cool pieces. I have never been in a small H&M, always upstairs and downstairs. I would say HM has that business casual and then that nightlife apparel. My advice is, use H&M like a just got a new job or have a semi-formal Gala coming up soon type of shopping trip.
Thrifting is one of the cheapest alternatives to the two I mentioned above. The possibilities are endless in what you can find thrifting. I remember a resident at my job found a Coach purse at our local thrift store and it didn't look half bad actually. I would say if you are looking for denim without breaking the bank stop by a thrift store, I bet you'd be able to find something that'll catch your eye.