I'm trying to beat the elite four,and I need to know 2 things. First were..

Ok, first things first. Get your team up by at least five levels and add a psychic or dragon type(i used chimecho and taught it awesome moves)(dialga works too). Second, get rid of Razor Leaf for something like grass knot, syhthesis, or solarbeam. Third, change slam to something like charge beam or thunder wave. And the best place to train... Victory Road of course! Hope I Helped!

Well the best places to train before th elite 4 really depends on what kinda moves you have. Essentially the best place overall is victory road, but the water to the north of sunnyshore city is fabulous for electric types. Now that is assuming you have full EV's. I would get rid of on of the fire moves on rapidash for flare blitz and maybe the other fire move for bounce or poison jab. He has better attack then special attack. Lucario will be ok if you have his nature and EV's set up for special attack. I guess torterra works, though stone edge would be better then razor leaf. Ive never been a fan of Crobats so Ive never used one but I guess yours is ok, may want to consider toxic. Same deal with raichu hes ok, but nothing special. Gyarados needs some work, he has a beefy attack and an abyssmal special attack, 3 of the moves you have on him now are special attack. Consider maybe waterfall for stab or other strong physical moves would be better. If you switch around those few moves and bring along a load of revives and hyper potions you should win with little problem

The best place to train them would be the water between sunnyshore and victory road. And victory road. Those are the highest leveled Pokemon to train against.

Use Rapidash to take out the first elite 4.
Use Torterra to take out the second elite 4.
Use Gyarados to take out the third elite 4.
Use Crobat & Torterra (bite) to take out the firth elite 4
Use all of them to defeat the champion

1. The best place to train would be in the Victory Road. Try rebattling trainers, too, using the Vs. Seeker.

2. To be honest, your team isn't that great.
You need to use a Fire, Ground, Grass, Fighting, Ice and Dark Pokemon to do good in the E4.
Rapidash would be your Fire. For Ground and Grass, your Torterra will do.
You need a good Fighting Pokemon, an example being Machoke or Machamp.
A good Ice and Dark Pokemon would be Sneasel or Weavile.
The last two Pokemon could be your choice. I'd use a Flying and a Dragon Pokemon, but like I said, it's your choice.

The best place to train you Pokemon is victory road the Pokemon are hard to beat but they are on high levels so they give lots of exp points thats how I got my Pokemon to level 100