1. Book a ticket from delhi to bhuntar from any private bus agency as there is no any govt. bus service from Delhi to Bhuntar, it will cost around 500-800 INR. It may be less in amount depends on which app you booked the ticket (you can also get promo codes if you are lucky) I booked my ticket from redbus app it cost me around 550 INR.
2.From Delhi to bhuntar it will take around 12-13 hour. When you reach Bhuntar enjoy tea, breakfast and admire the beauty of the nature. You'll have sufficient time to relax and freshen up because the bus service from bhuntar to kasol is at every half an hour, it will cost you around 40 INR and takes 2 hour to reach your destination.