Just timed this. I could never really get more than 50 gold without having to restart the app. So. I am currently sitting in group B in TTT. Weekly payout is 50k. 

Start the app with date on today. Run a TTT race and let the app do all the updates. Kill app and the start looking for the 'Welcome Back'. May take one or two spins but then get the 50 gold. Check the TTT. If there is no time remaining click on it and it will give you the payout. 

Go back and reset date to today, run another TTT and then kill the app and repeat. 

Gettin pg the rewards as above every time...