Freshman at UChicago studying Economics and Psychology
I did use a private admissions counselor for a bit, but I found them unhelpful and they just made me so much more stressed than I needed to be. There are many other ways to have your essays and activities checked, like through your own school, so there's really not that much of a need to be paying crazy amounts for an outside counselor.
I recommend taking AP courses that interest you because there is a lot of content to go through. If you are applying to American colleges, keep in mind that grades in the class are generally more important than the AP exam score.
Don't do a generic summer high school program that everyone does. Do something that makes you unique and niche. I suggest doing research if you're interested in that field.
I was self-taught from books and online resources. I bought SAT practice books and would look through them and practice alone.
The typical student at my school is an international student who is smart but low-key about it. We have 'cracked' athletes, a very diverse community, and students who are super ambitious.
I made sure to always quantify my impact and be specific. I aimed to be niche and unique in my descriptions. For example, for my tennis experience, I focused on specific tournament championships and regional awards rather than general participation.