Most of the dried herbs discussed in this thread can be purchased in bulk (many sellers also offer certified organic as an option as well) from ebay. A pound of dried herb can be purchased for cheap and should last a long time (assuming you store it properly). Some people I know like to mix dried herb with weed as well, claiming is smokes smoother, burns better and tastes better. I use damiana almost exclusively for mixing and for tryptamine-infusions cause I'm familiar with it and like that one, so can recommend that one but haven't explored many other herbs. In a pinch you can always use camomile tea.