You would like to keep your team high-leveled at all times, considering the game expects your Pokémon to be at least level 38 after the 5th Gym. The game is very fun and in my opinion one of the best in the franchise. I always pick Torterra because he's tanky and knows how to attack very well, besides its giant disadvantage against Ice. As my main bird, i've never used Murkrow but i adore Honchkrow. I always used Starly, Zubat or Togepi (It evolves into Togekiss in this Gen via Shiny Stone. Thing's beastly). For the Fire typing, i suggest Chimchar, Houndour or Ponyta. I always go for Houndour due to the great Sp. Atk its final evolution offers, but Rapidash, if used right, can be pretty deadly too. As for the Water type, i'm currently using Gastrodon and liking it. There are choices like Piplup, Buizel, Vaporeon and Shellos, among others. You might want to catch a Bidoof aswell, since it's a good HM Slave. Also Bibarel is neat. I used to dislike it, but now i absolutely regret my decision. And finally, catch a Gible under Route 206 (secret passage, might take you a while to find it) as it is very rewarding as a Garchomp.
Overall, a normal team for this is Torterra, Staraptor, Floatzel, Houndoom, and Garchomp. The last slot can be used for whatever you want. Hope i helped!
