For a second when I was looking at the title I was like, "what the HELL is a vaca?!" And then my brain clicked. BUT. I'd definitely bring a couple different swimsuits. Shorts, tank tops. That sort of thing. Sandals will be important. And, depending on what you're planning, perhaps some club wear.
Definitely get more than one bathing suit. You will want to have one clean to wear while the other one is being washed or dried. Also bring a couple pairs of flip flops, a cover up or two, and a nice maxi dress for the evening. Even a good beach towel or blanket to sit on would be good. And don't forget sunglasses and a hat.
Bring a nice dress in case you go out somewhere nice, some nice shoes, maybe a pair of flats. And some warmer clothing. Then just some basic clothes like shorts and t-shirts.
Summer clothes. I think you're old enough to figure that out.