I do like you - you are emphasizing that you like the person if there is any doubt.
A: I'm not sure that you and I are friends..
B. I think we are, I do like you!
I like you. - you are just saying you like them.
"I like you" is simple and direct and means what it says.
"I do like you" only makes sense as response to a challenge.
Person A: "I don't think you like me."
Person B: "I do like you."
Do i like you?
Does she like me?
I did not play to football
She does not love you
In present simple we do not need to use "do or does" when we say a statement
its like u mean it