@ab07 Good question. Based on what you said (good GPA & test scores, ECs lacking), here are two approaches you might take.
For the Common App personal essay, my initial instinct is to find a small, personal moment to focus on – these are what I call “little turns.” Maybe a moment of insight or turning point when you realized something about yourself: e.g., who you are, what you care about (i.e. value), how you see yourself in relation to others, or where you see yourself headed in the future.
If you write about a “small” moment like that, don’t worry about trying to be “creative” if that doesn’t feel natural to you. Instead, slow down and simply tell the story of that moment and what it meant to you.
You can use my Big Turns/Little Turns brainstorming exercise to try and surface some of those moments for yourself. It’s in my book, and I also put a free version of it online here: https://www.write-yourself-in.com/s/Big-Turns-Little-Turns-Chapter-4-l7g8.pdf
A second option, since your grades & scores are solid, is to ask yourself: is there a topic you’re particularly passionate about AND that you’ve pursued in some way, inside and/or outside the classroom? This is can be a good way to demonstrate intellectual curiosity, which is a top quality admissions officers are looking for.
Most of the time it works best to highlight intellectual curiosity in the supplemental essays. BUT if there’s something you’re particularly passionate about, and especially if there’s a story for how you discovered that passion, it can make for a great personal essay, too.
I hope that helps – good luck!