Most trainers can easily choose this adorable orphan from the lineup. The Cubone is a ground-type and a pre-developed form of the Marovak. It is particularly vulnerable because of this and is easily dealt with.
Thanks to Electiwire and Luxray sharing one type, this level of planning is a little easier than the next one. These are both Electric-type Pokémon, while Omastar is weird as Water and Rock-type.
This is the most challenging part of planning. Once again, Swampart and Tyranitar share a sort of weakness, the Grass-type, but they don't share it with the same severity.