I would switch aron for riolu for some more sweeping power and teach him for physical earthquake, close combat, ice punch, swords dance, special, aura sphere, psychic, dragon pulse, nasty plot.
Torterra is super powerful so do not give him up teach him earthquake, woodhammer/razor leaf, stone edge, crunch/swords dance/ rock polish.
Dratini physical waterfall/aquatail, dragon claw/dragon rush, fire punch, dragon dance special dragon pulse, flamethrower, thunder bolt, ice beam/agility.
tyranitar is awesome stone edge, crunch, earthquake, swords dance/curse/dragon dance/aerial ace.
Charizard physical earthquake, flare blitz/fire punch, thunderpunch, swords dance, special flamethrower, air slash, HP(grass), dragon pulse.
Swampert is also awesome in the top best starters with torterra and charizard. moveset for swampert waterfall, earthquake, ice punch/avalanch, stone edge/ hammer arm
out of all the types fighting, ground, and rock are super agianst the most leaving only 6 types, water, grass, ghost, dragon, fighting, and psychic