Actually, you can get rumble bags from rumbling, and also you get
two rumble bags for completing the first 2 badge sets. Once you hit
level 10 you start to get more things ^^
High key love rumbling. When I'm on an interaction break it's a
nice steady income source-- I usually average 7k-12k per 6 12-hour
rumble missions. Plus once you realize that all items they bring
back have uses, rumbling is pretty dang good for a passive site
feature. Free berries for interacting, free cooking items such as
soda pop and honey, gems, mystery items...
Just set 'em and forget 'em until you log in the next time.
I do love the idea of sending my mons out on little
walks/adventures, but I also wish there was some optional
interactions available. Possibly finding you more rewards if you do
interact.