Hey guys I just started what would be the best Pokemon to get before the..

Well for the first gym its the best you got mudkip, but for the others i took torchic and that was much less difficult. so i think the best is torchic.

Lotad is a good start, then Lombre and finally Ludicolo because it's a great annoyer. Nothing really is good to keep for the whole game, I changed my team a lot. You might want a Ralts to evolve into a Gardevoir.

Good question. Its nice to see people ask good questions like this instead of where jirachi and crap like that but anywho, the best Pokemon that you can find before the first gym that will serve you throughout te game is ralts. He is a solid preformer, especially at his final evolution which comes pretty fast actually. Others might depend on who you picked as a starter. There are good plant options early in seedot, who evolves to shiftry, and lotad, who evolves to ludicolo. I suggest not getting wurmple zigzagoon or poochyena, they all stink. In the forest some pretty good options are slakoth, a normal type who evolves into slaking, he can be kinda hard to use but he is a tank. Shroomish is another plant who evolves into breloom who is a big favorite of mine. And taillow who is infinitely better then stupid wingull. Saying that, most of the Pokemon you use in your final team will likely be obtained after this stage of the game, but you still have plenty of time to catch and raise them.

I'd say Ralts. They're rare outside of Petalburg, but worth it.