Using a grass type is good but if I remember correctly, Wake has a Gyarados. Now this thing is annoying. It's only real weakness is electric and if you plan on using something like Luxray or Magnezone you'll end up dead cuz they are not very fast (at least, not faster than Gyarados unless they are really high leveled) and Gyarados has earthquake. You do need a grass type for Quagsire because it is immune to electric. To kill Gyarados, you have two options. Either evolve that Eevee you can get in the city with the Ghost gym into a Jolteon with a Thunderstone from the Solaceon Ruins OR evolve your Monferno into an Infernape and teach it Thunderpunch (I'm not 100% sure if it's faster than Gyarados so that's a risk you have to take alone) by visiting the move tutor on the route south of the town with the Ghost gym. Either way, I think getting a Jolteon is the better choice cuz it's definitely faster and has great Sp. Atk and you can teach it shockwave which you should have gotten on your way here. To kill Quagsire, just use all your other team members and he should eventually go down. Or you could just get a grass type. The rest of his team should be relatively simple with an electric type. You could use Rampardos' thunder but it's highly unreliable and he doesn't get STAB for it either, plus he doesn't have the best Sp. Atk stat in the world either. Besides, in the longer run, having an electric type is better than relying on Rampardos' thunder. Furthermore, you don't even need a grass type. It has the highest number of weaknesses and everything it's good against is already covered; electric for water (if you take an electric type), water for ground and rock (Marshtomp) and that's it. But that's just my opinion.
PS: If you are going to get a electric and/or grass type, replace Hitmonlee since you already have a great fighting type who hasa better move pool and learns close combat sooner (Infernape).
Hope I helped.