Firstly, great news on getting good interest for your campaign. There are many ways to evaluate the incoming applications, some of the preferred criteria to consider include:
high engagement so you know which athletes have followers that engage with their post
a strong pitch that was personalized to your campaign and shows the athlete's enthusiasm to work together
value for money i.e. looking at athletes who are working within your budget despite being valued at a much higher rate
location, do you prefer to work with someone more local or someone who is in one of your target markets
We also try to help by letting you know which athletes are active on OpenSponsorship, and show you their rating if they have one from previous deals.