Pokemon GO follows the same basic formula of the handheld games and lets the players evolve each Pokemon. Charmander can be evolved to Charizard for example and Pikachu to Raichu.
If you want to make sure that you have the most powerful Pokemon available, then you will need to evolve each of the Pokemon to their final form. This can be done by feeding the Pokemon Stardust and then finally evolving them using their respective Candy type.
In order to gain experience points at a faster level, you will need to to gain access to an item called Lucky Egg. This eggs doubles the experience points earned and can be used at the time of evolution or capturing Pokemon to get as much as 200 to 1000 experience points.
If you want to know how to farm the regular and rare Candy, you can check out our guide here. Keep in mind that you will be rewarded Candy after you capture a Pokemon. The same applies to Stardust which is necessary to evolve the Pokemon with powerful stats.
Even if you have a higher level CP Pokemon, it is highly recommended to capture low CP Pokemon, especially if you are looking for a certain Candy type or want to farm Stardust for feeding Pokemon.
Pokemon GO is available now for the iOS and Android. It was developed by Niantic Labs and published by Nintendo.