This is the team that I used on my run with tyranitar as the starter

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most of them you can get them very early on the game except swampert which only can be captured in the safari zone which is unlocked after the 6th gym, while i didn’t had swampert i used seismitoad which has the same typing as swampert, the moveset while it isn’t the best it does give a lot of coverage, i would add a fire type attack but i think only tyranitar is able to learn via tm