There is a sticky in the changa subforums with lots of combinations listed! I personally enjoy either a bit of peppermint or lavender in a blend to make the smoke extremely gentle. Some of my other favorites include passionflower, blue lotus, calea zacatechichi, rosebuds, chamomile flowers, white lotus, Mexican tarragon... The sky is the limit.
If you are smoking through a bong, you'll want to light the herb for a split second, and then keep pulling so you can burn it with a nice and glowing cherry, vs. direct flame.
Happy changa explorations! It is quite lovely.
Some things will come easy, some will be a test