You could have a great time in a week but I would say 1 week is not enough to see Bulgaria.
With a week either :
- Hit up the 2 major towns. 4-5 days in Sofia and 2-3 days in Plovdiv and party your arse off or
- Hit up the black sea coast and split your time between Varna and Sunny Beach
With a week either :
- Hit up the 2 major towns. 4-5 days in Sofia and 2-3 days in Plovdiv and party your arse off or
- Hit up the black sea coast and split your time between Varna and Sunny Beach