With good researches (9/10), good gear, good castle, etc., it's possible to one shot RL lvl 3.
If you need several hit, if you have time, do it one after one to benefit of the iterative bonus.
In order:
Mountains clan exclusively.
Badges don't matter.
Sometimes, you will need to burn a +25% scroll to avoid to let some %hp. The most of time, don't burn it, keep it for good occasion.
“Dune fort” and “Last Heart” provide expedition bonus
For the troop march animation, you probably know the green smoke of “Kingdom Elite” (available in some shop, quite expansive) :
https://www.youtube.com/watch?v=L9gVVbK-PvY