Buspirone is one of those drugs that looks good on paper but is actually quite weak in practice. It's like moclobemide: it seems promising but in practice it's very weak. It's rated at 6.5/10 for anxiety on drugs.com: https://www.drugs.com/comments/buspirone/buspar.html
I think ashwagandha decreases 5-HT1A activity and partial-agonism is more-or-so the same - a net decrease in activity. From wikipedia:
when both a full agonist and partial agonist are present, the partial agonist actually acts as a competitive antagonist, competing with the full agonist for receptor occupancy and producing a net decrease in the receptor activation observed with the full agonist alone. [font=sans-serif]Clinically, partial agonists can be used to activate receptors to give a desired submaximal response when inadequate amounts of the endogenous ligand are present, or they can reduce the overstimulation of receptors when excess amounts of the endogenous ligand are present.[/font]
So in short, if you have sufficient serotonin already then buspar will act as an antagonist, but if you're low on serotonin then buspar can act as an agonist. Does ashwagandha antagonize the 5-HT1A receptor or does it just decrease serotonin while agonizing the 5-HT2A receptor?
Ultimately though, you have to take buspar to see if it's good for your or not. The only annoying thing about it is its short half-life meaning you have to take it 3x a day. if you do take it, let us know how it works out for you.