I am new to coffee and have recently purchased an aeropress. I know my question is subjective, but I would love to know what was the minimum amount of coffee grind that gave you a decent enough solution which you could have used to make a 200ml cup of Americano with.
I think you'll have to do the experiment to find out.
Measure the beans by weight rather than volume. A digital scale that resolves to 0.1 gram would suffice.
Use a binary search in order to converge on a result with as few trials as possible. E.g. if a reference scoop holds 8 grams, test 4 grams, then if that's too weak, split the difference to 6 grams, and so on. In only 5 trials you'll be able to get an answer to the nearest 0.25 grams; 6 trials to the nearest 0.125 grams.
If your goal is to use the minimum coffee to achieve acceptable taste, think ahead about how to judge if a sample taste is acceptable and how much time to wait between tastings for your mouth to clear. If your goal is to use the minimum code without noticeably changing the taste, use the triangle test.
Control the other brewing variables as tightly as you can: grind size, brewing water temperature (with a thermometer), water volume in the press and in bypass (Americano), brewing time, stirring amount, ... I think the most sensitive factors are water temperature and grind size -- and of course the batch of beans.
Please do report back!
It depends on your water. Using filtered water (carbon), 12.5g with the plunger about halfway between 1 and 2 circles and inverted is about right for me. Bloom, stir very lightly, fill to top, stir to break up clumps, flip, and press.
Start at 12.5g for 200mL finished volume and increase if drink is weak. If drink is bitter, you might have the right amount of coffee but waiting too long on the brew, or you might have too much coffee. You might also be stirring too much.