What is a good team for the elite four?

A good team would be one that consists of a Fire, a Grass, a Water, a Psychic, a Fighing, and a Bug Type, all that are at or above Level 55.

Hope this helps you!!!

Honestly, any team is good if you follow some basic guidelines.
1. Spread out your types! Don't have more than two (suggested that theres only one of each type) of any one type in you're team. 2. That also falls in with making sure that your team isnt too weak to one certain move type. I.e. Having a lucario, golem, and infernape in you're team MIGHT sound good considering my first point, but they're all weak to ground moves
3. Use as many dual types as possible, while following the last two points.
4. Don't bring any Pokemon under level 45, they will soon be useless (if they do good at all). I suggest level 55+ pokemon.
5. Buy ALOT of Hyper potions and revives, you'll love yourslef later. If you need more money, get the amulet coin, (Found in Amity Square in Hearthome city [Get a pikachu, clafairy, drifloon, psyduck, buneary, or happiny in your team and go to the back of the city]) equip it to one of the Pokemon you want to "train" (I don't think this will train it much, but it should already be strong) and use VS seeker on some trainers somewhere. You'll get alot of money that way. You could also go fight double battles at the resturant near Lake Valor with it and get MORE cash!!
6. Give them useful held items like leftovers or berries. Plates help too.
7. Teach them moves that help them defend against type trumps. I.e. Giving grass knot to your chimchar/monferno/infernape would be a good idea.
8. Using the new money you got, you could also buy some vitamins for your Pokemon (Protein, Iron, Calcium, etc.). That would be a GOOD idea.
Sorry for being so long...
Good Luck!

Have a fire type, water, ice, flying & dragon. My team was infernape, empolian, starraptor, garados, abomasnow

Make sure that your pokemon's weaknesses are covered by another's strengths. For example, a Staraptor is vulnerable to ice. You could use a fire attack to protect it. Also, try to have your Pokemon know moves that can defeat a type that they are weak to. Octillery is water type, but it can learn flamethrower(TM 35). My choices would be-Dialga/Palkia,Gyrados,Torterra,Staraptor,Gengar,and Weavile.

Level 60-100 Darkrai
Moves-Dream Eater, Dark Pulse, Dark Void, Hypnosis
Level 60-100 Infernape
Moves-Blast Burn, Heat wave, Flamethrower, Flame Wheel
Level 60-100 Dragonite
Moves-Dragon Rush, Fly, Fire Punch, ThunderPunch
Level 60-100 Raichu
Moves-Volt Tackle, Iron Tail, Thunderbolt, Dig
Level 60-100 Absol
Moves-Blizzard, Night Slash, Slash, Psycho Cut
Level 60-100 Gyarados
Moves-Hydro Pump, Aqua Tail, Ice Fang, Bite

Have a fire, water, psychic, electricity, fighting, flying. My team was infernape, floatzel, alakazam, pachirisu, lucario, staraptor. moves are:
infernape: close combat, flame wheel, flare blitz, rock smash
floatzel: aqua jet, focus punch, dig, water gun
alakazam: psycho cut, grass knot, recover psybeam
pachirisu: cut,super fang,discharge,thunder
lucario: extreme speed, dragon pulse, aura sphere, close combat
staraptor: fly, brave bird, close combat, defog