BHS BHS
BHS back layout step out
BHS back tuck
FHS FHS
FHS front tuck (definitely a cool one)
FHS front aerial
FHS BHS
FHS back tuck
FHS back layout step out
front aerial BHS
front aerial back tuck
front aerial back layout step out
round off BHS
round of back tuck
round off back aerial
aerial round off
I understand that quit a few of these are strange, but I can honestly say that I've seen/heard of all of these, and I'm fairly sure they all count as a level 9 series.
While you don't need to get "in the air" (ei: front tuck, back tuck, aerials) in level 9 just yet, a lot of gymnasts do them, and find them a useful way to get connection bonus.
Really, all you need in level 9 are two connected flight skills. Most gymnasts will do either a BHS BHS or a BHS back aerial, but it's not uncommon to see girls incorporating front handsprings or round offs into their series.
I can't say that all of these are at the same difficulty (if you can successfully do a FHS front tuck please tell me about it), but all of these should get you your series requirement.
Best of luck!