@Wagomu:
I get streaks on average over 10 using the Xurkitree I mentioned before. I supplement him with a couple dudes from my team, which are just a Muk and a Ribombee, and they sometimes come in handy, though I know my loadout could be better. Playing the Xurkitree well, alone, makes for some fast matches, but I got a Mild nature on it, so it doesn't last long if things go south. I just beefed him up with max SpAtk and Speed EVs, and gave him Electrium Z for thunderbolt. He can 2HKO almost anything on the tree with base SpAtk, and the Z attack lets him break through a lot of bigger threats and build up his stats with Beast Boost. His biggest enemies are sleep, focus sash, and anything that outspeeds him.
I'm running Hypnosis/Tail Glow/Thunderbolt/Energy Ball on him, but I'm thinking of switching Ribombee with Pheremosa when I get one, and removing Hypnosis for Dazzling Gleam, maybe removing Tail Glow for Volt Switch. Hypnosis has rarely hit anything, and I don't think I have to worry about boosting him anymore for the Battle Tree format. Even with this non-optimal set, though, I can get past 10 pretty easily, so I think it's a good start.
I'm guessing the EVs actually make a big difference, because with the stock one I don't do enough damage really, even with electric terrain. Volt Switch sounds good for flexibility (I did teach it to my Tapu Koko when I was trying out that combo), and Thunderbolt and Energy Ball make sense too for type coverage. Dazzling gleam adds even more type coverage. I can try that combo, though I still don't know if making it to the teens is efficient, but it's a start. I definitely need to EV train though, so maybe I'll get enough BP for all the power items then do that.
I actually also have a Muk on my team, in fact it's what I'm using for Battle Royal. But I have it set up for petty tactics (Minimize, Substitute, Gunk Shot and Knock Off, and a Black Sludge equipped). But hey who knows maybe that would work somehow. I'd probably toss in my Lucha Tigre as the 3rd just to test, after I train him too. He can do work, especially with the Z-Move.
@Kubihige:
I can trade a Bagon for a Geodude, Fool. Just let me know when you're ready to trade.
Sweet I'll let you know in a while.