Besides having a RED lipstick which I personally think that every female should at least own one stick
The next item I think every female should have and should own is
 A Mascara.
It's important that we always apply mascara to help accentuate the eyes
I don't know about you but but I love seeing expressive eyes
 That is why I enjoy looking at peoples eyes when
I'm engaged in a conversation with them. 

It somehow helps keep that eye contact better.
You don't really need to buy really expensive mascara, 

just use any brand which you are most comfortable with. 
Of course you will have to know that different mascara wand produce different type of end result
One coat of mascara on the lash and you can tell the huge difference 
Here is an image of a Before and after 

Can you tell the difference?
2coats on the upper lash and just one coat on the lower lash.
This is not a volumizing mascara I am using
Just the normal brush comb mascara.