You can manage four goals, but they must be useful to the plot.
So your overall arc is "growing up", selfish kid to mature adult, along with "coming of age" (sexual maturity).
The examples you have chosen are all selfish goals; but have the potential to transform into more altruistic goals.
1) [selfish] self-expression
2) [selfish] revenge
3) [selfish] making friends
4) [selfish] getting a girlfriend.
1) Transforming self-expression. Consider artistic self-expression a training ground. Entirely selfish, but for some reason (which we will get to later) this YouTube (YT) skill becomes important for another reason; an altruistic reason. Something happens (hooray a plot!) and his knowledge of what works and what does not on YT makes him the ideal prospect to expose corruption, raise money for somebody in dire need, help find a transplant donor. He can apply these YT skills to something besides self-expression, and succeed.
2) Transforming revenge pranks. Again, a training ground. What if these skills can turn into not just a prank, but justice? Suppose the problem is a thief, and his prank skills can make the thief reveal himself?
3) Transforming making friends. Friendships are often initially formed by a mutual self-interest. If you and I have a large overlap in the kinds of music we like, then by becoming music-buddies, we double our search-time for those kinds of music. I get for free your finds that I missed, and vice-versa. It is a win-win for us, and because we are humans these kinds of repeated transactions build friendly affection for each other; we may discover additional areas of interest in which we overlap, or beneficially complement each other. An example of complement might be on the YT front: Working on a video together, our hero is best at editing, but the potential friend is best at humor, something our hero lacks but appreciates.
Another area of mutual self-interest, of course, may be sexual attraction and sex, at whatever level of intensity you find appropriate; from holding hands to the various forms of intercourse.
4) Transforming getting a girlfriend. The adolescent idea of finding a mate are often extremely shallow, misguided and based on physical form; the boy wants the prettiest girl, or the girl wants the most dreamy guy. Those can actually work, as we've all seen in high school, the cliché of the football captain and the prettiest cheerleader became a cliché because it comes true so often. Both are shallow and appearance-driven, and enjoy being the "It" couple, but their egos (selfishness) get in the way of them having a loving relationship, whether or not they are having sex.
Growing into adulthood, whether at age 14 or age 35 or age 65, is giving up this shallow notion of an ideal mate, this masturbatory fantasy about a sex machine, to falling in love with somebody you care about. That often means realizing you are in love with the plain altruist girl trying to save the world, with real ideas you care about, and you are bored with the cheerleader that only talks about her trivial status symbols and who is prettier or who is the hottest actor or who has the hottest boyfriend.
The love interest is offstage most of the book.
I think that's a big mistake. If you don't develop her character early and often, she's just a prop; if she's just a prop, she is likely just the "cheerleader" cliché, a masturbatory fantasy, and while that may sell to young male teens, it is not much of a story, more of a wish fulfillment tale.
The transformation of "getting a girlfriend" from a selfish goal to a step toward adulthood is not satisfying a lust, but falling in love with someone. That requires a someone to fall in love with and that demands they be on stage often; in this case, he should have some significant interaction with this girl as the first turning point, about 15% to 20% of the way through the story, and be committed (not in love) to further significant interaction by the end of Act I: e.g. They are going to produce a video together.
That is the plot line I would use, here. The Cheerleader's name is Chandler; the Love Interest's name is Lindsey, (LI for Love Interest). The boy's name is Travis (to be TRansformed).
Your plot may be different, but here is an example of how to tie your threads together. It would still require quite a bit of invention and detail, but here goes:
Act I: Travis's normal, self-centered world. Lusting after Chandler, his ideal woman. Chandler wants to be an actress. She has a boyfriend, the school hunk, star basketball player or football player. State wresting champ or track star. (all physical, no intellect). Travis knows Lindsey, the girl with the posters, saving the Earth, saving the poor, saving the animals, fighting mayoral corruption, whatever. He doesn't really get it. Halfway through Act I: Lindsey seeks out Travis: She wants to make a You Tube video, something about corruption, and she has seen his. He's got skills, he can help. No, there is no pay, you'd be doing a good deed. He doesn't want to. Until he learns that Chandler is going to act in this video; she's going to present the whole thing! (out of selfish interest because Lindsey has convinced her this can be a good thing for her acting career). So he has a change of heart! Here is a chance to direct Chandler. It is selfish; of course, but he tells Lindsey it is for the good it will do. She sees through him, but takes his services anyway.
End of Act I: Travis is in, and you have your Crucible.
In Act II (50% of the story), Things don't go as planned for Travis. Chandler is a shallow bitch. He works beside Lindsey nearly every day. He gets infected by the facts she has uncovered, this corruption thing is no small deal, this politician or cop or church leader (the offstage villain) needs to be in frikkin' JAIL, he is hurting people.
Chandler doesn't give a crap, she wants better lines. She wants a scene where she can kiss her boyfriend because maybe she could play a romantic leading lady in a rom-com. She over-acts her part and isn't happy with Travis's direction or his dailies.
Other people Lindsey has recruited for the video are better, they care, (becoming his friends). They get it. And Lindsey: Lindsey is a force of nature, and amazing. He can't stop thinking about her, he's up in the middle of the night working on her video, trying to devise scripts, short and sweet but getting the message across, video and music and lines Lindsey will like, but she's tough. It isn't easy.
ACT II ending: Lindsey loses Chandler. Chandler is bored, the video is crap because she may be beautiful but she's a lousy actress that can't deliver a straight line without trying to put something on it. And besides that, all they have is a bunch of inconclusive evidence. On a Saturday Lindsey brings Travis to meet her father, an attorney, they watch the film so far. Her father is kind, they could show it, but he doesn't think it will have any impact.
In private (but with her father in the next room), Lindsey tells Travis she is giving up. Spontaneously she hugs him, tells him he was great and more than she hoped for, but ... she messed up by casting Chandler. She thought a pretty face would help, but it just ruined everything. Holding back tears, she tells Travis, "See you at school, director." She turns away and leaves the room.
Travis doesn't know what to do; in a moment he leaves, going home.
Travis is in love.
Act III: Dig in to climb out.
Travis won't give up. All day and night Saturday and Sunday, he's going through his clips. He finds video of Lindsey trying to give Chandler direction in saying her lines --- Which means Lindsey is saying the lines. He's cutting them together; Lindsey can do the presentation. He's cleaning up the sound, and putting it together. He doesn't have half what he needs, but he wants to prove it to her. She's perfect. Why were they wasting time on six takes for every line by Chandler when Lindsey is the queen of nailing it in one? Was he crazy?
As for a smoking gun: Travis has just the prank for that; a secret audio recording. (or something similar we show in Act I as a prank on someone). but now for real against an actual criminal. He won't tell Lindsey, he'll just do it, and leak it to her anonymously.
Travis gets her on the phone Sunday night. Don't give up. Look at this (his cut together tape of her). I don't want you to give up, we can reshoot this whole thing.
Lindsey resists; she's not an actor. But eventually they do.
ACT III finale: Travis plays his prank, it works. He devises a way to get it to Lindsey on a thumb drive; anonymously.
I am a discovery writer; so my endings are provisional sketches and may change, but I think for this plot, this would be a suitable provisional ending for me:
Lindsey holds up the red thumb drive.
"Is this yours, Trav? Did you do this?"
Travis looked at the ground, then met her eyes, pleading. "I don't want to lie to you, Lindsey. Don't make me lie to you."
Lindsey closed her fist around the thumb drive, then changed her mind and held it out to him. "Feel it, see if it feels like one of yours."
"Feels like? What are you talking about?"
"For once, don't argue with me."
Travis takes the thumb drive. "Okay. Maybe. They all feel the same!"
He hands it back to her. She takes it, and puts it in her pocket.
"Yeah I guess they do. My dad will say we have to give it to the police. I think they'll fingerprint it. Maybe look for DNA. Of course they'll find mine and yours and probably my Dad's, but maybe somebody else's."
Travis choked up. She was protecting him. "Do I ruin everything if I say I'm in love with you?"
Lindsey folded her arms and looked down, shaking her head, but with a small smile, then she met his eyes. She unfolded her arms, her hands up and open at shoulder height.
"Try it and see."
Like that.
