This level I didn't find too challenging, and you probably won't either as long as you've been keeping up with your training at least a little bit. What I found to be most important for this level was having a Geodude/ Graveler/ Golem in the middle square (on the rock) that knows Magnitude. This deals a pretty good amount of damage to the bosses, as well as the other pokemon in the level, with the exception of Spearow and Zubat. Magnitude is based on luck though, so you may catch a couple unlucky (or lucky) breaks. Other than your Geodude/ Graveller/ Golem, you should have your next strongest pokemon in the middle spot, and then 2 more on the left side of the map and 2 on the right side of the map. I would put your starter in the middle, because it is probably your strongest pokemon, but a Butterfree with Whirlwind is just as good of an option, if not better. Butterfrees using Confusion are good pokemon to fill the rest of the slots on the map since Butterfree's Confusion attack is a special attack and most of the pokemon in the level have high defense but not special defense. A Pikachu with Thunderbolt is also not bad, since it can take care of the flying pokemon that your Geodude/ Graveller/ Golem can't hit. However, be careful because some pokemon in this level don't take any damage from electric attacks. My suggestion is to use a mix of Geodude (or its evolutions), Pikachu, and Butterfree. These pokemon aren't too difficult to get, and can help you win the level. Mankey is also very useful for this level, as its fighting attacks do 2x damage to Geodudes, Rattata, and Clefairy. This level is only 9 waves, and when I played it, I didn't let any pokemon even reach the candy. Just take advantage of the opposing pokemon's weaknesses, and your pokemon's strengths. This level shouldn't be hard for you, but the upcoming level Mt. Moon 2 likely will be.
Catchable Pokemon: Zubat, Geodude, Clefairy, Rattata, Spearow, Mankey, Ekans (Red), Sandshrew (Blue)
Level Difficulty: Easy