In my opinion, you should visit golden temple twice. so the day you reach there, go to golden temple at night. you will find a cheap and good accomodation not so far from there. next morning, go to the golden temple again. I would prefer you to go between 5 and 6 am as there will be very less people there. also, keep one day for visiting the Wagah border. It's a long and tiring journey, but the experience is wonderful.
and on the last day, you can visit places like Jallianwala bagh, gobindgarh fort etc.
PS. Do try the local food. it's one of the best in India.