If you want super-effective moves against the majority of the trainer pokémon here, bring pokémon that know Fire, Water, Grass, Fighting, Bug, Ice, and Rock moves.
Pokémon that you can catch here
One of the first things that you'll notice about Route 7 is the very tall grass. There are some trainers hiding out in here, and, of course, there are plenty of pokémon hiding in there, including Watchog, Zebstrika, Foongus, Deerling, Tranquill, and in the winter, Cubchoo. Shaking spots might be Audino, Unfezant, and Emolga.
Trainers, items, and more
One feature of Route 7 are the narrow raised ledges that go over the grass. The key to walking on the ledges is to keep moving. If you stay still for too long on the ledge, you'll lose your balance and fall off into the grass below.
Be sure to speak to the Battle Girl who is walking around on the ledge near the entrance to Route 7, because she will give you TM57 Charge Beam.
One of the first trainers that you encounter is Backpacker Terrance who has an L31 Simisear, which is weak to Water, Ground, and Rock moves.
In the tall grass near the entrance, you will find Youngster Mikey, who has an L30 Dwebble, which is weak to Water, Rock, and Steel moves, and an L30 Simisage, which is weak to Fire, Ice, Poison, Flying, and Bug moves.
Also in the tall grass, you find Youngster Parker, who has an L29 Palpitoad, Shelmet, and Scolipede.
There is an Ultra Ball in the grass near the youngsters.
Farther along, you will encounter a house where someone will give you an Emolga in exchange for a Boldore. There are plenty of Boldores in Chargestone Cave to the south, so catch one there and bring it to the guy to get your Emolga if you wish.
Triple or Rotation Battle
Then there is a ledge to the right of the house. Once you get down from it on the other side, you meet Ace Trainer Elmer who does a rotation battle (if you're playing Black) or a Triple Battle (if you're playing White) with you using an L32 Liepard, L32 Watchog, and L32 Swoobat.
For the rotation battle, all three of his pokémon will be out at the same time, but only one will be active at a time. He can rotate the active pokémon with the others on a turn, or he can have the active one use a move. The tough part about this is that you will have a hard time using super-effective moves against his pokémon because he might switch out the active pokémon before your attack hits. As long as you don't use pokémon in your first three slots that are weak to any of his moves, and as long as they are strong enough to withstand his pokémon's attacks, you should be able to make it.
For the Triple Battle, it's pretty straightforward, and you will be able to hit his pokémon with super-effective attacks. However, you still will want to make sure that none of the first three pokémon in your party are weak to any of his pokémon's moves.
Continuing on Route 7
North of the Ace Trainer is Backpacker Ruth, who has an L31 Minccino. Use Fighting attacks.
North of her is a PP Up in the grass, and a couple of Pokémon Rangers. The southernmost ranger is Mary, who has an L30 Swadloon, Tranquill, and Simipour. North of her is Pedro, who has an L31 Solosis and an L31 Axew.
Northeast of Pedro is a Max Ether in the grass.
Near Ruth, there is a ledge leading to a house. Inside, the woman near the TV will heal up your pokémon for free.
If you go up the stairs that are to the east of this house, your Mom will call on the XTransceiver, giving you some words of encouragement and advising you to take good care of your pokémon.
You can continue east if you wish, where you will fight a couple of Harlequins, but you won't be able to go any farther than Route 7 in that direction. Instead, head north from the Pokémon.Rangers to find Celestial Tower.