Right now SPS has very few use cases. Staking for getting more SPS and Vouchers and entry for tournaments.
The Splinterlands team has commented that in the future we will see more uses for SPS, such as voting rights for future changes in the game. I also believe that there will be more uses wich are not known even by the development team. Im long SPS but also hold a decent amount of DEC for the airdrops.
For now acumulate SPS, they give it for "free", then in a couple of years ill decide my next step.
Enjoy the game!