leveling up

If you have the vs battle item then use it to see if there are trainers that wish to re-battle you. Or you may just have to battle wild Pokemon till you level up, or use rare candies.

Try this.Spend a lot of time in one place just training pokemon.You can train in the one spot and it should level up your Pokemon as you battle.Try to get stronger wild Pokemon to face.

You may just have to take a few minutes on your own time in a good patch of grass and raise each of your Pokemon a few levels. I can get kinda boring and tedious but it's worth it. Heres a hint I don't think most people have taken advantage of, go to route 209 and fight wild Pokemon there. You can occasionally find chanseys. If you have a Pokemon with the move theif, and a little patience you can have the biggest payout ever. Put your thief in front and run from anything thats not chansey, use thief on chansey. It will be holding oval stone like half the time, but 5% of the time it's holding a lucky egg, which multiplies the exp gains by a Pokemon holding it in battle by 1.5... This basically means that you can raise a Pokemon 50% faster with the egg then without. Give it a shot it will be a good way to gain levels quickly

Well, for Maylene, I would suggest using a Starly/Staravia/Staraptor; she uses Fighting types, which is weak against a flying type. Using a Staravia or Staraptor is reccomended, at least in the upper twenties or lower thirties. Teach him Aerial Ace and Close Combat.

Now, for training, such as your Starly, you should focus on one Pokemon at a time. Train that Pokemon against anything that comes in your way, and for best results, try to train in areas with Pokemon as the same level as you. Or, you can use the Vs. Seeker against trainers. Just keep battling. You'll eventually get to where you need to be.

Use the Vs. Seeker to rebattle strong people, find a good patch of grass, or use rare candies.