POCO is sometimes used wrongly, because in Italian it can have a negative connotation, meaning “not enough”:
Ha pochi amici
He doesn’t have many friends
Ha fatto poco per me
He has done little for me
But it doesn't always have a negative connotation:
Meglio avere pochi amici ma buoni
It’s better to have few good friends (rather than lots of bad friends)
At a dinner party, you might want to say to the hostess:
Poca pasta per me!
Not too much pasta for me (please)
UN PO’ means “a bit of”
What are you eating?
-UN PO’ di dolce (a bit of cake)