Hi...I used to be a big tomboy myself, and only really started wearing makeup when i was 25 (27 now). I still don't wear a lot. I suddenly became interested somehow. I don't wear much - just wanted to know how to apply it, and i do think a little goes a long way.
So, I think the minimum for others who wear a lot might be a lot for you. Brow powder is always listed as an essential, but frankly, I used to use it a lot and I like the way I look without it better. I do look more natural without it, and if your brows are already well defined, I think you can skip that.
Also...I still don't wear foundation. If you take good care of your skin, you don't really need it. A lot of people could have better skin if they didn't use conventional foundation. I have a foundation i like that I use as a concealor to hide dark circles or a zit. I like it better than regular concealor because you can build it and it isn't as thick. Foundation all over the face is a bit much if you are trying to go minimal. I would stick to concealing dark circles and zits and using a transluscent powder.
I would just wear mascara on eyes if it were me. I use an eyelash curler then apply mascara and it makes a nice difference. sometimes i dab on a shimmery neutral toned eyeshadow on my lid, which also hides imperfections. i just use my finger. i actually think it looks better than when i use a brush.
some days i just wear powder, conceal spots, and wear a red lipstick. I think it's a nice contrast. A lot of guys have told me they like that look actually...a more or less bare face and eyes but emphasizing your lips.
so for me -
- foundation or concealor to conceal imperfections only
-powder
-mascara
-a neutral shimmery eyeshadow
-and a lipstick you really like
not all at once, but you can play around. i wear very minimal makeup myself.