I began my PokeQuest with Chimchar, the fire monkey, and soon added a Geodude, Shinx and Shellos to my crew. Geodude, who evolves into Graveler and then Golem, is a rock/ground Pokemon who is impervious to electric attacks and stands up well against flying and fire Pokemon. His Magnitude attack wipes out all kinds of opponents, but he is useless against water and plant enemies.
Chimchar, the Diamond and Pearl answer to Charizard, is a cute monkey with a flaming tail. When he evolves into Infernape, his hairdo goes flaming, too.
Hence, I also have Chimchar, who burns through plants. For fighting water Pokemon, I captured a Shinx, which evolved into a Luxio who evolved into a Luxray—a relatively competent electric Pokemon.
You should always strive to have the basics—fire, water, ground and electric—in your party. You can combine elements (Gyrados has fire and water, Infernape has fire and fight) but you need to cover your bases.
I generally do not carry ghost or psychic Pokemon. I know, there are a lot of you out there who will swear by Alakazam and Mewtwo. But you can teach Luxray Bite—a dark attack that wipes out psychic and ghost Pokemon in a hurry.
Get your water, electric, ground and fire attacks down pat, and you will have an answer for any situation.
Tips from Nintendo
In Pokemon Diamond and Pokemon Pearl, the way Moves affect opponents have changed. Physical Moves strike the opponent up close and use the Attack stat, where as Special Moves strike from afar and use the Special Attack stat. Knowing the difference between the two greatly improves your battle strategy.
Have your Pokemon learn moves that cover its weaknesses. For example, have a Fighting-type Pokemon learn a Ice-type or Dark-type move.
Pay attention to a Pokemon’s ability. Quite a few Pokemon have more than one available to them. A Pokemon’s ability like Levitate can make the difference in a battle.
If you have taught your Pokemon the wrong move, don’t fret! There are people in the Sinnoh that can help. Try looking for the Move Deleter or a Move Tutor. These are people who can help you with your troubles.