OED's first definition is apparently the oldest sense (but now obsolete)...
1a: a going, journeying; course, passage, way; voyage. (cf thoroughfare)
...which transparently leads to the still current sense...
4b: cost of conveyance (now only of persons; formerly also of goods); passage money
I should point out that I consider usages such as How are you faring? to be dated, bordering on archaic. The other primary sense that's still current (fare = food, provisions) seems to have been arrived at through these (now also obsolete) meanings...
6a: mode of proceeding, bearing, demeanour; appearance, aspect.
6b: a proceeding, action; ‘doings’; hence, fighting.
6c: display, pomp; commotion, uproar, fuss
7: Condition, state, welfare; state of things, prosperity, success.
...ending up with OED's final definition for the noun usage...
8: food, regarded with reference to its quality;
supply or provision of food, regarded as abundant or scanty.
I think that final sense arises through mode, aspect in the context of journeys which would be long enough to need provisions - of a quantity and/or quality commensurate with the fare = price paid for the fare = journey by the fare = paying passenger.
Note that from the point of view of the person/company providing the transport/provisions, both the paying traveller and whatever he will need to eat are things that have to be transported that wouldn't normally be called "cargo" (because they're not for sale at the end of the journey).