If you have one essay which is due prior to when the others, start there. Otherwise, focus on the essay for your top choice school. I would also recommend starting with a longer personal statement before moving forward to shorter supplementary essays, since the 500 – 700 word essays tend to take quite a bit longer than 100 – 250 word short responses. The brainstorming you are doing when it comes to long essay may allow you to come up with ideas you want when it comes to shorter ones as well.
Also consider whether some of the prompts are similar enough you could submit the same essay to multiple schools. Doing this can help you save a while and enable you to give attention to a couple of really great essays rather than plenty of mediocre ones. However, do not reuse essays for dissimilar or very prompts that are school-specific especially “why us” essays. If you are asked by a college to publish about why you’re excited to go there, admissions officers like to see evidence you are genuinely interested. Reusing an essay about another school and swapping out the names may be the fastest way to prove you’re not.
Example: Eva’s College List
Eva is applying early to Emory University and regular decision to University of Washington, UCLA, and Reed College. Emory and Reed both utilize the Common App.