Ricky Fitts is definitely an odd duck—and that's probably putting it mildly. At first, we think he might be odd in a psychopathic way, because he's videotaping Jane (and others) without their knowledge. It's hard to be creepier than that.
Once Jane strikes up a friendship with him, though, we learn that Ricky's actually just pretty sensitive and artistic. He likes filming things so he can capture the beauty in the world around him, which he sometimes finds in surprising and morbid places. For example, Jane comes upon him filming a dead pigeon, and he ends up showing her a video of what he believes to be the most beautiful thing he's ever filmed: a plastic bag blowing in the wind.
RICKY: It was one of those days when it's a minute away from snowing. And there's this electricity in the air. You can almost hear it, right? And this bag was just dancing with me. Like a little kid begging me to play with it. For fifteen minutes. That's the day I realized that there was this entire life behind things, and this incredibly benevolent force that wanted me to know that there was no reason to be afraid. Ever.
He also finds beauty in Jane, which is definitely more understandable. As they get closer, he opens up about his difficult past with his family. Apparently, his dad sent him to military school after catching him doing drugs, beat him when he got kicked out, and then put him in a mental institution when he acted out after all that. Despite all that, since Ricky really is a sweet kid, he swears he doesn't hate his dad.
(Drug-Dealing) Paradise Lost
Ricky has tried to keep the peace at home by striking a balance: he does everything he can to make his dad think that he's straightedge (you know, not doing drugs or anything like that), but he still does drugs and deals them.
As you might imagine, with that big of a deception, it eventually falls apart—although not necessarily for the reasons you'd expect. Frank spies on Ricky and witnesses him providing Lester with drugs.
However, Frank doesn't actually realize what he's seeing—instead, he thinks Ricky is performing oral sex on Lester. He's just as freaked out about that scenario, and when he confronts Ricky angrily and violently, Ricky decides to leave home forever.
It's obvious that both of them are upset about how the situation plays out, but Ricky—since he's super confident and wise—manages to see that his father's wacko behavior is coming from a place of pain, and calls him a "sad old man" in parting. Sad indeed, but Ricky seems so completely confident and able to suck up the good from any environment or situation that we suspect he ends up being okay.