In Pokemon Go, which moveset for Jellicent in PvP has the highest win rate result?

I recommend PvPoke for determining ideal movesets in PvP based on win rates. It ranks Pokemon against each other based on their match-ups against the rest of the metagame, with match-ups against more popular Pokemon being given higher priority. Each Pokemon is ranked based on its moveset that gives it the best overall match-ups. It gives different match-ups and ideal movesets for each league, including some special cups like Kanto Cup.

At the time of this post in each of these leagues, Jellicent's ideal movesets in the main leagues are:

• Great League: Bubble, Bubble Beam and Shadow Ball
• Ultra League: Hex, Shadow Ball and Ice Beam
• Premier Cup (Ultra without legendaries): Bubble, Bubble Beam and Shadow Ball
• Master League (normal and Classic): Hex, Shadow Ball and Ice Beam

Ranks and movesets can change over time. By default, these rankings assume that both players have 1 (and only 1) shield. This setting can be changed manually. Further details can be found on their site.