A couple of years ago, I created a sort of system that has helped me greatly in designing movesets, and I thought I'd share it with you all.
The system is designed to numerically rank the overall effectiveness of an attack type, in the most basic sense. Each type receives a set of three numbers for ranking. Here's an example:
Ground: 15-5 (20)
The first number represents the amount of types this type hits with a minimum 1.0 effectiveness. The second number represents the amount of types from the first number that are hit super effectively. The third number, of course, is the combined total, which marks that type's rank. The ranking number does not necessarily specify superiority or inferiority, but rather that type's most basic range of attack effectiveness.
The system can be utilized in a number of ways. The most prevalent way is moveset ranking. When a moveset is created, tallying the ranks of all attack moves will result in the rank of that moveset. Below is an example:
(NOTE: The following is merely an example and does not reflect any viewpoint of gameplay.)
Hydro Pump Ice Beam
Blastoise's moveset contains two attack moves, Hydro Pump and Ice Beam. Hydro Pump, being a Water-type move, has a rank of 15-3 (18). Ice Beam, being an Ice-type move, has a rank of 14-4 (18). Combining the two ranks without any overlapping, Blastoise's moveset rank comes to 17-7-1 (25).
In the most basic sense, Blastoise can hit 17 types with a minimum effectiveness of 1.0, and it can hit 7 types super effectively. The extra number, 1, represents the amount of STAB types within the moveset. Since Blastoise is a pure Water-type, its moveset can never have a STAB rank higher than 1.
Of course, in the battlefield, dual typing plays a strong factor in the overall effectiveness of a moveset, or any attack at all. This is why the system is designed in the most basic sense, to prevent confusion. However, once the system is utilized, it becomes much easier to calculate the effectiveness of whole movesets against any dual typing.
The system's type listing is below, adjusted to the current generation.
Normal: 15-0 (15)
Fire: 14-4 (18)
Water: 15-3 (18)
Electric: 14-2 (16)
Grass: 11-3 (14)
Ice: 14-4 (18)
Fighting: 12-5 (17)
Poison: 13-2 (15)
Ground: 15-5 (20)
Rock: 15-4 (19)
Flying: 15-3 (18)
Psychic: 15-2 (17)
Bug: 11-3 (14)
Ghost: 16-2 (18)
Dragon: 16-1 (17)
Dark: 15-2 (17)
Steel: 14-3 (17)
Fairy: 15-3 (18)
I hope this system can help you all as much as it has helped me. Thanks for reading.