The tiles are the same as the one in the starter kit, so you can indeed go for a second starter kit if you need more tiles. It's more cost-efficient. Unfortunately, the price is based on the one we get from our supplier.

yes that should work i only have both on one connection

The difference is that the Starter Kit includes a small HUB to which you plug in the Master Triangle, which then controls the lighting. There are 2 connections on this HUB, so you can easily connect a Starter Kit and an Expansion Kit to it.