UCs usually rule out students if they have below a 3.5 (I may be wrong, just speaking from experience). For your essay, I’d consider focusing on only one or two activities and associating them to how they built your character and aspirations. If you do more than one activity, make sure they are relevant in the context of your essay. Also make sure that you don’t just end up listing every accomplishment you’ve made– this is the reason I’m emphasizing just focusing on one or two programs you were part of. It’s good to be concise so you can focus more on how YOU are coming off in your essays, not just your accomplishments on paper.