If you enter in the lvl 50 or lvl 100 battles, your pokemon will be automatically set at that level, no matter what they are in reality. So you could do a lvl 100 battle and your turtwig (I'm guessing it's actually Grotle?), Murkrow, Buneary, and Buizel will all be lvl 100 in the battle.
However, if you want to do wi-fi battling... you've got a lot of work to do. If you want to be competitive and not just get your face smashed in, you're going to have to breed for IVs and Natures, EV train, and design a 6-pokemon team that works well together with strong pokemon. See the Strategies & Movesets forum for help on all of this.