must haves, whatever else you get, you should have
foundation/tinted moisturiser - I shall read with interest as still not found a foundation I like but I found Clinique barely makeup or whatever it is called quite good.
Under eye concealer/corrector - i am still struggling to find one I like that does not cost £25 a pop but i really have to have something under my eyes to soften the darkness. Whether you need this depends on how heavy your eyes look.
mascara - I am happy with no.7 long lashes or something like that, but a good quality one whatever you get.
lipgloss - this is where I spend too much money. My favourites at the moment are 'Motherplucker' by Soap and Glory, tinted gloss. I have two Clinique gloss which have lasted me forever (clear and 'natural'), and my most prized possession is Chanel Levres Scintillantes natural tint. Gloss is the best thing in the world as it can turn the most tired un-make-up adorned face into glamour.
In addition to this, as I have red skin, when I am going out (rarely these days), if i have a moment before work, or my skin is particularly bad, I wear No.7 Colour Calming Base (green one) under foundation/tinted moisturiser, and a natural lip pencil to define my lips a little more and maybe some soft green/brown eyeshadow.
I tend to wear makeup to make me look naturally healthier in my face, rather than to look glamorous. But even on days I wear no make up at all, a it of gloss makes the world of difference to how i look.