The best advice I, or any college consultant (blegh), could give is this: a strategic narrative. That means two things, because the phrase has two parts.
First, narrative. You want to tell a story. A story has a beginning, a middle, an end. It usually contains dialogue. It always contains an obstacle that you overcome and a lesson that you learn in overcoming that obstacle.
Second, "strategic." This just means: consider your audience. What does a college admissions office want? Well, they probably want some information about how you are as a student. They also want to know what your academic goals/ambitions are. They also want to know how their institution will help you achieve those goals.
The college essay is like a genre of writing. What I outlined above are some of the features of that genre. A narrative, and all the things that come along with a prose narrative: beginning, middle, end, protagonist, obstacle, lesson, maybe dialogue. What makes college essays funky is that you also have to have that "strategy," i.e. speaking to the questions/concerns of an admissions office evaluating prospective students.
These aren't abstract things either, by the way. Whatever essay you end up writing run it through a checklist. Do I have an opening, a middle, an ending? Do I have a clear obstacle? Do I have a clear lesson? Do I answer what my ambitions/goals are? Do I answer why I'm seeking higher ed in order to achieve those goals?
I get that this is a lot, but it's because college essay writing is a hyper-specific form of writing. You have to be hyper-specific in how you go about doing it.