One blaze rod unlocks the whole potion system. From a single Awkward base you can brew speed, healing, fire resistance and a dozen more, in three bottles at a time.
Swiftness
Healing
Fire Res.
Strength
Awkward base
Brew nether wart for an Awkward base, then branch to Potion of Swiftness
The recipe
A blaze rod over three cobblestone. The blaze rod means a Nether trip comes first.
Three cobblestone is nothing, so the entire cost of a brewing stand is one blaze rod, and blaze rods only come from a Nether fortress. That single item is why potions are locked behind a fortress trip rather than behind a level or a village.
Blaze powder is the fuel and it is not optional
The stand needs powder in its own fuel slot to run, separate from any ingredient. One rod makes two powder, so the same fortress trip that gets you the stand should get you a stack of rods, because running out of fuel mid brew is the usual reason a first potion setup stalls.
Three bottles at once, same ingredient
The stand brews all three slots together with one ingredient, so brewing in threes costs the same as brewing one. Any potion setup that is not filling all three bottles is wasting nether wart, and nether wart is the ingredient you will run short of first.