I will be replaying Ultra Moon for the first time in a while. Here is the the team that I will use:
Incineroar @Incinium Z
Fire Punch (Move tutor)
Darkest Lariat (upon Evo)
U-turn (TM)
Brick Break (TM)
Salamence @Dragonium Z or Amulet Coin
Dragon Claw (Level up- Lv29)
Fly (upon Evo)
Zen Headbutt (Level up- Lv35)
Roost (TM)
Sylveon @Fairium Z or Soothe Bell
Moonblast (level up- Lv37)
Shadow Ball (TM)
Echoed Voice (TM)
Draining Kiss (Level up- Lv20)
Metagross @Steelium Z or Leftovers
Meteor Mash (Level up- Lv 45)
Zen Headbutt (Level up- Lv 32)
Brick Break (TM)
Iron Head (Move Tutor)
Araquanid @Waterium Z or Mystic Water
Liquidation (Move Tutor or Level up- Lv57)
Leech Life (level up- Lv 33)
Bug Bite (level up- Lv13)
Crunch (Level up- Lv 38)
Cradily @Grassium Z or Big Root
Ancient Power (level up- Lv 17)
Giga Drain (level up- Lv 26)
Brine (Level up- Lv 21)
Energy Ball (Level up- LV 44)
My reasoning for choosing each Pokemon:
Incenroar:
Incenerorar is my favourite of the three starter Pokemon in Alola. I haven't used it since I first played for Ultra Moon which for me was six years ago in 2018 when I was almost thirteen. It also has a wide move pool in regards to both TMs and Move tutor moves. Also the attacks it levels up learning will be instrumental against the totem battles, Molayne in the league, Faba's Psychic types.
Salamence:
Salamence is a pseudo-legendary that I have never used. I want to use it for the first time because not only is it veyr good but it can also Mega Evolve when I am able to access the Battle Tree in the post game. It will be a long way to go to get it to it's final evolution but it will be worth it.
Sylveon:
My favourite Pokemon of all time. I use it at any opportunity if my starter isn't a fairy type, hence why I picked Incineroar. Also I chose to run echoed voice on Sylveon because a) it is stab when it is an Eevee, and it increases in power with each consecutive use.
Metagross:
Metagross is here for the same reasons as Salamence. I have never used it before, I can Mega evolve it in the post game and I know it will worth it. I also am trying to expand the Pokemon that I use, and I always like using a psychic or steel type, and Metagross is both of those. I know it will be a pain to get, having to wait until the third Island, but I am willing to make that sacrifice.
Araquanid:
Araquanid is one of my top 3 favourite Alola-native Pokemon and I know that it is a totem Pokemon in Ultra Moon, which is super fun because I like collecting the totem stickers. Araquanid also has a solid BST (Base Stats Total) of 454, which is not the highest, but it can be a monster in the right hands, and I should know. When I first played Pokemon Sun in 2017, my friend Taylor would sweep me with an Araquanid, which made do the same in my first copy of Pokemon Moon in the Autumn of 2017. Anyway, enough reminiscing, Araquanid will be the defensive wall of the team, and I don't mind the ability I get, though I will probably prefer Water Bubble as it turns the neutral fire matchup into a resistance.
Cradily:
Cradily is my favourite fossil Pokemon. It also makes a nice Grass-Fire-Water core with Araquanid and Incineroar. I know that Grass/Rock is a very good type combo, and, yes, I know Brine isn't a typically good move, but it does provide some coverage for ground and fire types, which I know is Araquanid's job, but the more coverage the better I say.