Swalot @ Black Sludge/Leftovers doesn't matter does the same thing
252 HP/ Defense and Special Defense investment are up to you depending on what the teams needs, special or physical defense.
Stockpile
Infestation
Toxic
Protect
honestly the best thing I can see for him is a good Toxic stall pokemon, the stats just aren't there for attacking so focus on the bulk and shut the opponent down by trapping him and putting on the toxic timer.
gimmicky but honestly there's not much you can do with him in the meta
