Body powder recipe

Hi,

I want to make a body powder to keep sweaty regions dry.

I plan to base it on something I buy where the major ingredients are cornstarch (maize) – readily available in the supermarket & silicon dioxide (safe in this form and readily available online).

Does anyone have any advice on what proportions I should mix these two ingredients in?

If adding essential oils to powder, do I just add some drops to a container of powder and shake?

Thanks for any advice.