Okay that outfit is not very. Good. But some people may not understand why.
First off, when designing an outfit, the general idea is to stick to 3 colours. The statement piece, which is the drippy top, already has three colours. The 3 colour rule does not include black and white given how technically they are not colours but tones.
Green numbers are our statement piece, white ones are the pieces used above to "complete" the outfit. If you want to add more pieces to the outfit, you stick to the above hues, and preferably similar brightness and saturation. We're in a zone of slightly desaturated pastel, making use of a bright red beret pointless, additionally you already have a statement piece, which fucks up the balance.
Now to make loose suggestions based on whatever clothing pieces I'll quickly find on Pinterest on how to style this, using the same silhouette since that's something I actually do like about the outfit. That's it though. Just the silhouette.
Let's make several suggestions, starting with full pastel since that's the easiest choice here.
Not the best outfit of the century but I put this together in 2 minutes let me be. Either way whoaaa far more balanced and better looking no wayyyyy. But you may ask, Andria you dickhead fashion snob, what if I wanna draw even more attention to the piece, what if I want contrast to be present. And to that I say. Remember now there are different tones and shades of different colours? Mhm. Now check this shit out.
Holy fuck. Brightness. That's a thing. You make shit dark. So let's run with that now. So we have some blue purple fuckery going on. Perfect. You know what else comes in blue colours? Pants. Which pants? Denim. So here's what we end up with when we go for higher contrast:
Somehow ended up going for a cute little spacey theme but here we go. Not much else to say I pretty much described it above.
All in all, the thing I saw far above with that person's attempt at finishing the outfit is just common mistakes. "You MUST have an accent colour" advice and the beret and plaid not quite business not quite casual not quite business casual pants. I've been there buddy but yeah there we go I don't know how to end posts, just know it isn't a burn on anyone, just an explanation.