Preventing trainer from going somewhere based on badges

I am currently working on a game, which starts in the Kanto, and New Island is to the south of Cinnabar Island. I have placed a building directly below the Island, and I need to have a liaison of some sort to prevent the trainer from passing before getting their 8th badge.

Also, I'd like to figure out how to lock up the last gym until the first 7 badges have been collected.

Thius is more for essentials section but anyway, no script is required just use switches or Variables.

Variables sounds better, in my head.

Step one: Create a variable!
Step two: Each time you beat a gym leader variable +=1
Step three: If variable < 7, the door won't open!

This shouldn't be too hard too implement. If you're strugglinh with this, try looking up some basic RMXP eventing tutorials/exercises before trying to tackle similar, or even more difficult problems.

Doesn't Essentials come with a set of "Defeated Gym X" switches anyway? You can turn those on after beating every gym leader.

Variables would probably work much better for things that require a specific number of gym badges to be obtained, for example entry to the Pokemon League would require a check of 8 by standard. Things which require individual badges, such as small roadblocks, should use switches. I doubt you'd want to set an 8-tier conditional branch for a Pokemon League checkpoint, and I doubt you'd want to have a roadblock cleared from a route that required the "Third" gym badge, but you instead have a variable set to check for "Three" gym badges.

Variables for larger things, switches for smaller events.

$Trainer.numBadges is how many badges the player has. Everything else is RMXP knowledge.