If anybody else, like me, is struggling with easy farming Battle Tree points to get breeding items because they can't breed yet, then maybe you, like me, also didn't know that Ultra Beasts are allowed in the Battle Tree. SubSalac Xurkitree seems like it should be a huge help in blasting through the lower levels for some quick points to buy Destiny Knot and evolution items.
you get 50 BP per run on basic battle tower (20 battles), you then unlock real battle tower, for that ruleset.
Battle royal can net you 5 per battle.
UBs and Tapu are not legendary or mythic, no restrictions!!
top VGC teams have all included a Tapu (lele or koko, some bulu) and at least one UB; kartana (focus sash) or celesteela(leftovers/leach seed)
Other newer OU picks would be Ninetales (hidden ability, then aurora veil), Marowak (lightningrod, trick room use), Megalith(Sand stream), Peliper (drizzle, tailwind), Muk (knock off), Araquanid (there is a hidden secondary effect on its ability, bonus water damage)
Muk, kartana, incineroar, toxapex, and decidueye have the battle tree ribbon for me...
still own 0 destiny knots, have done pleanty of relatively successful breeding (am relying a bit on my bottle cap supply)