Its a lame question but a question nevertheless. Anyways it depends on ur needs. I studied in FAST-NU so basically used Laptop and a diary only. No books etc. So i bought a NIKE shoulder bag last year, the ones usually kids take to the school, but it was comfortable and decent. It can hold 2 or 3 books and a diary if u r not carrying a laptop. Since u r in lahore, goto the Nike store on Main Blvd and check bags there. They usually have sale on all bags there at this time since all universities and school/colleges open now. U can either get a discount or a free cap worth rs 800. Now that was last year so im not cent percent sure but they should have discount this year aswell. I chose a bag worth 2000 and got it for 1400 after discount. Now another thing, my bag didnt have a discount sticker on it but i learned bot it after i went down to cashier to pay so ask before u buy it. As for quality well ive used it in worst way possible and still its in excellent condition.
PS: Congrats on getting admission in LUMS. Its a prestigious uni and i sincerely hope u do well there.