Griggs is the only "friend" that we ever see with Richard. He’s also the only person who gives Richard advice instead of just ordering him around. You could say he’s something like a big brother to Richard, although his advice isn’t always the best. He tells Richard, "Dick, look, you’re black, black, black, see? Can’t you understand that?" (1.9.70)—which may be true, but it’s not exactly inspiring.
Basically, Griggs schools him in how to act black. Griggs reveals to Richard the secret socialization of blackness that he apparently never got taught. In other words, sure, Richard is black. But he has to learn how to walk, talk, and act like a "real" black person because he’s apparently not acting like he’s black on the inside, too. If you’ve ever heard someone called an "Oreo," and we’re sorry if you have because that is totally racist, then you know what Griggs is talking about.
Here’s the problem. Griggs may have figured out how to get by in the white world, but it’s not exactly helping him. He still has to resort to stealing to make enough money, and this just isn’t the way Richard wants to live his life. As a smart, savvy dude, Griggs is an example of what Richard could be like if he’d given in and acted the way everyone wanted him to. But he can’t.