for the breeding question it depends, are you realy that fussed on natures because it can take awile to get the right one. if you want to, then thats fine, but it will be quicker not to.
well your pokemon like you alot more if you raise them yourself and it honestly doesnt take that long if you train on victory road and rebattle trainers. if your pokemon like you, you can get some good items and if they get confused in battle, they will snap out of it quicker and wont hurt itself if it likes you more. plus its really rewarding training your own pokemon!
are you going to evolve turtwig and staryu into starmie and torterra?