The best moveset for Arbok in the current competitive meta typically features the moves Breaking Swipe, Protect, Coil, Gunk Shot.
In the Pokémon Champions meta, Arbok can be countered by exploiting its weaknesses (ground 2x, psychic 2x) and using effective check/counter teams.
The best item for Arbok is typically Hard Stone, based on high-level tournament and ladder stats.