Best type of hosting for building a network

Hello. I am planning on using the tools here to build a WordPress network. Something similar to WordPress.Com Currently I am on a shared hosting plan and it works great and will probably work great for a small network of sites. The thing is I am wonderin what would be the best type of hosting for this solution, that will keep all sites loading fast and easily allow me to scale up
if it takes off. I don't know much about hosting so I'm hoping you can help. Thanks so much!