OK since you're on budget similar to most of ppl here..My recent trip of 6D4N can be used as guideline. I EXCLUDE hotels & air ticket bcos already paid in advance. You can prebook hotels using the link on 1st page (innotel, hostelworld or agoda)
Wth the AAX tickets & hotel excluded, I changed ~RM2170 cash into Won (well to USD 1st thereafter won). Yesterday, I changed back the whole US$218 available and got back RM680

So total spending only ~RM1500

AND this was for 3 persons!!

(Avg exchange rate at 2.85)
Rough idea of how I spent my RM1300 there (for 3 pax)"
- T-Money 33,000w X3 but got back 3600w X3 at the end of the day. (~RM260)
- Daily food for 3 X3 (Brunch & dinner - some meal simple convenience shop kimbap & drinks

) ~ 12,000w X2 X3 X 4 nites (~RM820)
- Souvenir, entrance tickets, Taxi & etc ~180,000won (RM520)