I am interested by both Japanese and Chinese cultures and I intend to learn both Mandarin and Japanese at some point (I don't even know if this is realistic as I also intend to learn Spanish and German) and I would like to know if there is any advantage with starting with one over the other as I know that Japanese has imported many Chinese words and symbols but they have also changed and evolved over time.
I already have experience on how to learn a second language as I am a native French speaker who's learned to speak English and took Spanish lessons for a while in High School.
FIY: Among the reasons for learning both languages is a strong interest in Zen Buddhism and it's origins, the game of Go and martial arts, so that might interesting to keep in mind in your recommendations.
Thank you all very much in advance!
P.S. This may already have been discussed to death in other threads. If so, please forgive me.