a bunch
You cannot get all 3 Starter Pokemon in Pokemon Emerald without trading for the other 2.
You migrate it from Ruby, Sapphire or Emerald. You get it from those games via Mystery Gift event.
In Pokemon Emerald, Eevee and Poliwhirl can only be obtained via trading...
There is no way to get Mystery Gift without using the Wireless Adapter. Sadly, the events for Pokemon Emerald are expired and there will be no more events for this game.
All if you have a gameshark
you can migrate him from emerald or sapphire.
gameshark code
you can't.
beat the battle frontier!
Get Pokemon emerald and then you can get all three without cheats or trading
Pokemon Emerald 386 is a hacked version of Pokemon Emerald that allows you to complete the pokedex without trading and/or hacking. It's a ROM that can be played on a VBA. You can get it at 4shared.com.