Moves
Bulk Up allows Gogoat to tear through teams and remediates its more or less uninvested Attack and Defense stats. Horn Leech is Gogoat's go-to attacking move, hitting Ground-, Water-, and Rock-types hard and providing a reliable source of recovery. Substitute is a good way to avoid status and makes setting up on walls much easier. Additionally, the recovery from Horn Leech negates the lost health. Earthquake is a great coverage move that hits Fire-, Electric-, Poison-, and Steel-types. Rock Slide can be used for valuable coverage against Fire-, Bug-, Flying-, and Ice-types, but typically Gogoat can beat those either with another move or with the help of another teammate.
Set Details
252 EVs are put into HP and Special Defense, maximizing Gogoat's special bulk. A Careful nature is used to further bolster Gogoat's Special Defense. Leftovers is used for a reliable source of residual health. Lastly, Sap Sipper is used to beat opposing Grass-types and get an Attack boost at the same time.
Usage Tips
Gogoat can come in on most Water-, Ground-, Grass-, Electric-, and Rock-types, such as Prinplup, Lilligant, Kabutops, Rotom, and Sandslash, and proceed to set up either Bulk Up or Substitute. It should watch out for Scald burns from Water-types, however. Before trying to sweep, you should dispose of Pokemon carrying Taunt. If Gogoat can get a few boosts, it should try to spam Horn Leech, as even if it is resisted, it can wear down foes quickly.
Team Options
Water-types such as Samurott and Carracosta work well as teammates, since they beat troublesome Fire-types, while Gogoat can beat Electric- and Grass-types for them. Fire-types such as Pyroar and Magmortar make for good teammates, as they beat Bug- and Ice-types, such as Vivillon, Scyther, and Jynx. Additionally, Gogoat can handle Water-, Ground-, and Rock-types in return. Gogoat, along with Fire-type and Water-type teammates, form a good core that handles one another's weaknesses. Garbodor makes for a good teammate, as it can deal with annoying Pokemon such as Vileplume for Gogoat, all the while setting entry hazards. Lastly, Ground- and Rock-types such as Sandslash and Kabutops make for good teammates, as Gogoat can beat troublesome Water- and Ground-types for them, respectively, as well as Grass-types, while they beat Bug-, Poison-, and Flying-types in return. Additionally, both can spin away entry hazards that can threaten Gogoat's ability to set up.