don't think you need to worry too much about the ingredients..
as the trophy says you just need to find one of each.
so I think just actively taking on animal form once in a new area.. should be fine.
hopefully!
there's a guide on the 360forum for the statues that is pretty good,
a little confusing sometimes, but definately better than nothing
and for the animals, they are rarely hidden (so far)
just the castle levels you have to keep an eye out, some are in the houses and
the yellow sliding doors.