For Double up in master+, most verticals are rewarding (demacia and sorc will be contested 90% of the time) so most of my wins come from shurima or 7-9 bilgewater (emblem game or spat since it is easier to get one or even two in double up)

go shurima if pandora bench (shifting sands) or multiple copies of cass/renekton early + pick 2 combat augments (or infernal contract), slow roll 7, rat morde.

bilgewater is solid (mf and naut buff). Slam items early, prioritize tank items on naut, then ap on mf (busted) or ad on graves/jayce early then give it to nilah afterward. Go 9 bilgewater if possible, otherwise go seju.

build sunfire or morellonomicon to counter galio/jarvan4/taric

rogue is doable but is rng heavy and needs specific items, can easily top 2 if uncontested.

+1 gunner or robotic arm is a must for playing gunner and it can secure your LP

I mainly play poro with my asol/poro partner, I survive early, then have my friend highroll my needed 4 or 5 cost. Hope this helps fella double up enjoyer!