right now all i have in my built on flash and whenever i take a picture at night it comes out all grainy and bad. if i get a good flash will it make the pic look not grainy
Grain or noise shows up at higher ISO settings and when your exposure isn't good. A good flash will give you more flash power and the ability to create a better quality of light for your subject...but it won't directly give you less noise.
It would help us to help you, if you could post an example shot along with the shooting information.