Just to clarify, I'm recommending those herbs to experiment with, not combine all together!

Also have this written down from somewhere as a guide to mixing:

Base (40-80%): Mullein, damiana, mj

Leading herbs:

Psychoactive: mj, damiana, sinichuchi, blue lotus

Dream enhancement: calea zacatechichi, blue lotus, mugwort

Cognitive: gotu kola, passion flower, ginko biloba

Stress: damiana, skullcap, chamomile, hibiscus

Mood/Depression: Lemon balm, motherwort, skullcap

Flavouring(5-10%): peppermint, chamomile, lavender, sage

You can infuse ipa with flavour herbs (or any herbs), especially those like lavender that can be harsh to smoke.

Skullcap, damiana and passionflower work well together.

Shouldn't forget Pau d'arco, but I'm not sure which category that would come in? Mood maybe?