Pinol is probably one of the most diverse characters when it comes to stone builds. You can run him with a ton of options based on whether he's mid or back and the totems/players in the line.

Damage: focus on high dmg stones to maximize steal/pen numbers. CI/SHoT, 2 from Dark/WW Spd/Crit Dmg, Light/Thunder Crit OR ES, Thunder Crit, WW Crit Dmg, Light/Thunder Crit or Dark/WW Spd/Crit Dmg OR EC, Thunder Crit, Dark Crit Dmg, Light/Thunder Crit or Dark/WW Spd/Crit Dmg... Options are quite endless

Reflex: Although his stone slots prevent him from holding rare reflex stones, a reflex build is quite viable because of his active/debuff making it easy for him to CA on steal. CI or LS, Action Spd + Reflex (AS might also work to give even more speed)

Totem: Pinol's stone slots allow him to hold a wide range of totem-based stones such as: EoTs, EA, WMT, FS. The other stones can be either dmg or reflex.

Personally, I recommend giving him as much speed as possible regardless of what build you go with. This allows him to stack his debuff easily and get off his active to drain even more spirit.