14 years of age is fine…
I think anything shocking is wrong unless you are at a club/ or a fancy dress party. Enhance/Accentuate is the name of the game… If say for example you have acne, a medicated concealer or tea tree oil underneath concealer and a tinted moisturizer in case you have some discolorations you don't like and a powder for shine on the nose is good to cover up something you don't like.
Then after that, maybe some brown/black mascara to make the eyelashes look darker, and a light bronzy/pink/reddy lip gloss/tinted lip balm or even a lipstick like cliniques almost lipstick is good. Maybe some bronzer or blusher.
Anything under 10 is not good. Tinted lip balm or light pink or clear gloss is fine for the pre-teens, between 10 and 13, according to the age - preferably tinted lip balm/chapstick for the 10-11 yr olds and clear gloss for the 11-12 yr olds, and then light pink gloss for the 12-13 yr olds.