In one famous conversation ( reported by Jean Wahl, among others) in Paris - it was considered that you could look upon an apricot cocktail on the cafe table in front of you and build a philosophical account of Reality from there.

Our experience of air can be a start - we feel the breeze on our skin and when it's going through our hair ( on the scalp, if one's bald!), and then it's getting pulled into our lungs, and is expelled back in an automatic way.

Attending and becoming more keenly aware of air - invisible, apparently non-material, and almost attribute-less - which as breath is our primary sign of life, it should be possible to embark on an authentic exploration.

After fifty pages, you could always refer to some Milesians who defined Air as the fundamental element of the Universe, and eastern and other philosophies who have theories and doctrines around it - but a proper start would be with one's own direct, uninfluenced examination which cannot be substituted by study of other scholars, regardless of how revered they are.