Doing those will unlock both the National Pokedex and the Poke Radar. You can use the Poke Radar ... which increases the chance of a rare encounter. As the chain continues, it gets more likely ...

While you’re hear, make sure to pick up the Chain Counter, which will track your catches. Next, you need to pick a Pokémon you can find in the wild. Choose your Pokémon, load up on Repeat ...