Question: how to get 3 starters in pokemon emerald?
Answer: You can only get one of each starter in Ruby, Sapphire and Emerald. The rest have to be obtained by trades with other players. Unfortunately this means in order to get Torchic, Mudkip and Treecko on the same team at a time, you have to hope someone bred the starters you don't have and is willing to trade with you.