It depends if you want to start powerful, start weak or normal. If you want to start powerful but end as a weak trainer, choose Treeko. If you want to stay as a good trainer all the way to the end, choose Mudkip. If you choose to start a bit weak, but end as a powerful trainer, choose Torchic.
I reckon it is a better idea to start with Torchic, because the trainers are very weak at the start but strong at the end.
its your starter. if u dont pick it, you cant get it
you get either Pokemon sapphire or ruby and you link and restart the whole game on ruby or sapphire pick out a Pokemon and get to a Pokemon center and link to the other gba and trade for another Pokemon and repeat like twice
trade
no you can catch a charizard in pokemon ruby you can get it as a kanto starter
You should use either Groudon or your Starter Pokemon. I used a crobat and a garados.
first you pick treeko as your starter. then you beat the elite four. then you look around hoenn forhim
Mudkip is available as a starter pokemon in more than one games. They are Pokemon Ruby, Pokemon Sapphire, Pokemon Emerald, Pokemon Omega Ruby and Pokemon Alpha Sapphire.
mudkip
Torchic, Mudkip, and Treecko.
trade
you can't.
Entei doesn't have a specific location, but they are roaming around Kanto after you beat the E4, get the National Dex, and give the Ruby and the Sapphire to Celio. The legendary dog that runs around Kanto is based on the starter that you pick. When you pick Charmander as your starter, Suicune roams around Kanto. When you pick Squirtle as your starter, Raikou roams around Kanto. When you pick Bulbasaur as your starter, Entei roams around Kanto.