Looking for help with marketing and getting users for a custom t-shirt project

Hello everyone,

I have created a website(VeeFitt.com) where one can print a custom t-shirt based on their workouts on Strava. Strava is Facebook for athletes. Athletes post their workouts on Strava.

I have an Instagram account where I have posted couple of pictures. I have promoted them three times. I have not got even a single user sign up from Instagram.

But when I posted on Reddit, 45 new sessions that day and 15 users connected their Strava account and one of them bought a t-shirt.
https://www.reddit.com/r/Strava/comments/ewrvrm/hello_everyone_i_recently_made_a_webapp_that_lets/

Some ideas I have is:

1. Regularly post on Instagram using Strava hashtags and promote it
2. Like pictures of people who have a hashtag of Strava in their picture
3. Message people using #strava on Instagram

I am looking for strategies, channels and other ideas where I can get more users to connect their Strava accounts on the website on a regular basis.

Thank you