I would normally be a casual and say to reset until you get a good nature... but I wouldn't want to continuously capture something with a 3 capture rate.
You could always breed for the proper natures & IV's / moves you desire.
You have to mine rocks for them. You get the mining kit underneath the grand stairway after defeating gym #4. If you choose to not, you can get one in Pyrous Montain after gym #5.
Hello Wakeless & welcome to the Reborn forums. be sure to introduce yourself in the Grand Hall if you have not already.
As you were asking, Growlithe is a pretty good Pokémon, but you can get Numel on the Pier where you first start the game on a rainy day with PokeSnax in your inventory.
learns some pretty good moves too
You can also get Houndour eventually around the 4th gym & Vulpix from the Salon in Obsidia
After that I think that's it for a while
You could always start a play-through in Episode 9 which many people have the download for, and get a Togepi Egg before the second gym from a Quiz in the Coral Ward.