Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
We have a Golduck analysis in progress now. There's a lot of Pokémon out there, and many of them are not viable at all, so it takes a long time to get an analysis up for every single one. You can anyways inquire on irc or a specific metagame's subforum to get an idea of some usable strategies.