[X] Start with Wrap then use Thunder Wave, then keep using Wrap, and Leer - Staryu has the advantage at range, take advantage of its moment of vulnerability, and don't let it get away. It also wouldn't hurt to end the fight as quickly as possible by using Leer on the paralyzed Pokemon well Dratini puts the squeeze on it.
[X] Start with Wrap then use Thunder Wave, then keep using Wrap - Staryu has the advantage at range, take advantage of its moment of vulnerability and don't let it get away