When you give a homeless person 50$, that makes him feel pretty good, to a large part because he feels like somebody is watching out for him. But of course that is also based on the joy he imagines from spending that 50 bucks on things that he likes. After all, if you didn't give 50$ but 1ct, you'd be giving the same gesture, but it wouldn't actually help him. At the end of the day, if you care about someone, just making him a gesture that you "care" won't change much, to really show that you care would be to also helping him get happy in more direct ways.
Interpersonal connections are important, but once they become circular, they start to become kind of ridiculous. Let me give you an example: For Christmas, without having arranged this beforehand, I give my brother 200$ for him to buy himself an XBox One (I can't buy myself my preferred consol, the PS4 now), who in turn gives me 200$ of his money, for me to buy a PS4. In a way we both showed each other great admiration and caring, by giving up something just so the other can get something he enjoys. But at the end of the day nothing actually happened, so we basically just made a nice but empty gesture to each other, which hopefully made us feel good.
Don't get me wrong though, not all happiness comes from material things. Quite the contray, I believe most things that truly make you happy are interpersonal, whether they're social skills that make for a great conversation or just the feeling that somebody else cares about you. Social skills, though, are also in a way "materialistic", all skills are We wouldn't say that watching a skillfull theater performance isn't "consumption of work", and in a way neither is having a fun chat with a stranger in a train. They're obviously done for very different reasons, but still they're only enjoyable because the other person has a skill, not because we inherently enjoy hearing that person speak.
In House of Cards, Claire complains that so many women think the meaning of life is having children, giving up everything for them. But what if those kids grow up to also want to sacrifice everything for their kids, and they for theirs? It's just an endless cycle of caring at a great price, without anything deeper being accomplished. And if spending quality time with your kids makes you feel good, like a drug, then how is that fundamentally a "more legitinate way to get happy" from "real" drugs? In a way "unconditional love" is less personal than conditional love, right? If you knew someone loved you for your personality, you may like that more than if somebody liked you just because he likes you, right?
My point is, the more you think about life and the meaning of it, the less things really means anything, the less anything appears to "make sense". If you try to read too much meaning into anything, you'll find that it has much less of it than you hoped for. But why does life have to mean something "on the grander scale", isn't it enough if we just live our lives and are happy for some unexplained reason, even if there's no magical "greater cause"?