During the early Renaissance, how might a knight-errant equip themselves to mitigate the offensive capabilities of flying, fire-breathing reptiles?
It can be assumed that the knight, backed by a wealthy benefactor, would have the funds necessary to procure multiple sets of full plate armor. However, they might choose to spend this money on different equipment should such armor prove insufficient to the task (for example, one might invoke the imagery of a tin-wrapped baked-potato to illustrate the potential downfalls of metal armor).
It can also be assumed that dragons are a relatively well-known threat. Furthermore, the fire-breath of the dragon in this scenario is produced by combustible gases (rather than petroleum jelly or some napalm-like liquid you might find in a flamethrower), such that the flame is unlikely to "stick" to objects that do not immediately catch fire.