Well you picked Blastoise so Gary will have Venusaur. You could go to Mt. Ember and get a Magmar. Or level up that eevee a bit and evolve it into Flareon. Or you could level up Hitmonchan a little. Its many punches with many types can be helpful, but if you dont want to go through a lot of training Magmar would be a good addition to your team. Or of course you could go to Seafoam Island and get Articuno or get Moltres at Mt. Ember. (I wouldnt recommend adding Zapdos if you go with one of the legendary birds because you already have Raichu. If you have money and can buy a lot of Ultra Balls I would go for one of the birds. Don't use your masterball. I would save that for Mewtwo.