there isn't really a best team i find a team with well balanced types i know the best team to use on the Pokemon league is just a blazeiken and a salamence so that might work on the battle frontier aswel and with that a good water Pokemon and that should work
Any Pokemon strong to water: Electric types and grass types work the best.
There are 3 types that work best against psychic Pokemon: Bug,Rock,Ghost, and Dark.
There are several types that work well against Rock-Types. Water and Grass are the most commonly used against them, but Fighting pokemon, Ice and Steel works as well.
There are no required types for your Pokemon team. The choice and variety of Pokemon types you wish to incorporate in your team is entirely up to you. Some teams might benefit from a grass type because the presence of one would increase its "synergy" or how well the Pokemon work together. Other teams might not require one at all. Once again, you can choose ANY Pokemon to be in your team. Sometimes, though, one might be better than another.
Types AGAINST water (e.g. Your Charmander attacks Squirtle): Super effective (double damage): Electric | Grass Not very effective (half of the damage): Fire | Water | Ice | Steel Water against types (e.g. Your Squirtle attacks Charmander): Super effective: Fire | Ground | Rock Not very effective: Grass | Water | Dragon If you want to defeat a team of water pokemon, you need grass pokemon and electric pokemon. Be sure to avoid using water pokemon, ice pokemon, fire pokemon, and steel. It may be best to also avoid using ground and rock types. If you have a water team, and don't know what types of pokemon this team will work best on, you'll find that ground and rock pokemon are easy to defeat, as well as fire pokemon. Against ground and rock, damage is multiplied by four. Fire pokemon may be harder to defeat if their second type is dragon.
Ice types.
Take a mixed bag of Lvl50+ Pokemon.Water types work best and fighting and poison types would be screwed if you bring them out.
Your starter Pokemon and a friend bow I recruited Groudon with just Blastoise and a friend bow and that seemed to work (P.S. Blastoise was NOT my starter Pokemon)
That's for you to decide. Obviously you would have legendarys, all level 100, and make sure you have all the important types (fire, water, grass). Lets just say it wouldn't be easy to get the best team, but it would be a fun work in progress.
If you're talking about Jasmine of Olivine City, then Fire, Ground, and Fighting-types are your best bet. Water-types also work for her Steelix. Stay away from Ice and Normal-types. :)
Ground Types work the greatest.