It actually isn't that easy! I try to never use any legendaries, but had to use a magearna this time. Trick room is a reliable strategy, and got me to the 5th battle quite frequently. I mainly led carbink to set it up and for some utility/ chip damage, then dealt damage with alolan marowak or magearna. Thing is, for any strategy you choose you will find some teams that counter you, so you'll likely need some tries. A mon I had tried and gave me incredible results was wobuffet, guaranteed kills in 1v1, if in trick room may take 2 thanks to destiny bond.
Other strategies you may use would be electro web galvantula, or a prankster screen/terrain setter, and then a set up sweeper, giving maybe a berry for status conditions.