Gases are compressible. The harder you push, the smaller a gas gets. So volume and pressure must be inversely related.

Heating a closed container is never a good idea (unless you're looking for trouble) and a balloon in an oven will expand while one in a freezer will shrink. So volume and temperature must be directly related.

Certainly blowing more air into a balloon will cause its volume to increase so the volume and the number of moles of gas must be directly related.

Each of these early gas laws includes important restraints: whichever of the three variables (pressure, temperature and moles) is not explicitly mentioned must remain constant for the law to be valid.