1. Can the personal trainers you’ve onboarded become ambassadors of the app?
a. If yes, and if you have the ops/tech means to execute a commission-free model for clients booked through/acquired by your ambassadors (think unique affiliate link, tied to said ambassadors), then try running it for 1-2 months aggressively (basically, leverage your fitness trainers to bring onboard their clients/customers to your app)
2. If in-person bookings > online bookings, identify supply-side hot spots (where you have the highest concentration of personal trainers) and get out there on the streets to hand out flyers, talk to your potential users, or even onboard them on the spot (if the sign-up process is seamless) during lunch and after work timing. Camp outside the gym/fitness studio and catch outgoing gymers if you need to
Both of the above initiatives aren’t costly and can be executed by the founders themselves. Keep all the budget for referral rewards and to partially incentivise repeat bookings if necessary