Can anyone tell me how to get each of the 3 starter pokemon. Has it got something to do with breeding?
There are very few ways to get all three starters with just one game.
The first (and probably easiest way) is the GTS. Located in Jublilife City, the GTS allows you to make specific trades via Wi-fi. Normally, people will ask for starters or legendaries for starters, but if you keep refreshing your search, you will likely find one for something you have. (I say refresh because good offers get taken fast.) If you were lucky enough to get a female starter, your quest has been simplified. Breed it with any compatible Pokmon, and you will get a baby of your original starter. You can put this up for trade for another starter. (If you have a male, you will not be able to breed it unless you have a Ditto.)
The second way is to organize a definite trade with a friend or online. Sometimes you can find a person friendly enough who will just give you a freshly bred starter Pokmon for pretty much nothing. I