As of the 15th of October 2016, the servers for this game were shut down and all achievements are now discontinued.As of the latest update, you can only send 3 free spins every 4 hours!
Not updating this game to v1.2 allows you to keep sending unlimited gifts. You will however still only receive 5 spins as this was updated server side.
There is no limit to the amount of "Free Spins" gifts you can send to eachother, so just keep sending them to the same friend over and over and ask them to do the same.Free spins that you randomly receive in-game (not from friends) count for this as well. Thanks
https://www.trueachievements.com/Jappe+XBA.htm for confirming.