Is the VIP shop worth it?

This is a matter of opinion, but once you complete zone commemoration technology, you'll have more teleports than you can use. I use my VIP to buy iron, cash or cores, and big convenience items like the ability to rush all of my resources with one click. It also offers might and resistance buffs, for each troop type. It's another resource you can tap to get items or resources, which is helpful, but it's definitely not required.