In this video I go to both Mun and Minmus with a single Kerbal X rocket, for a "flag and footprints" mission.
The Kerbal X only have 6428 m/s of delta-V, so I optimized each aspect of the mission, trying to spend the bare minimum delta-V each time.
I wanted to do it without any mod, but realised that it would result in more than half of the video being on the map view. So as a compromise, I installed KER, but with only the orbital information that you could get normally. I also added the delta-V stats, so I could present you the delta-V budget (vacuum) :
Low Kerbin orbit : 3130 m/s
Mun transfer : 858 m/s
Mun 10x5 orbit : 275 m/s
Mun landing : 599 m/s
Mun 10x10 orbit : 585 m/s
Minmus transfer : 207 m/s
Minmus 10x5 orbit : 87 m/s
Minmus landing : 221 m/s
Minmus 10x10 orbit : 198 m/s
Minmus to Mun gravity assist : 99 m/s
TOTAL : 6259 m/s