A switch will only allow network to talk to each other via "up", not receive information from the web, "down". So you need a router to route the internet, hook up the router outputs to 4 hubs or switches that those 30 hosts will connect to the hub or switch. The router will just divide up the internet connections. This should take care of your network hardware needs. Let me know what you think and how it goes.

You are going to want to use a switch. the reason you will want to use the switch is because of the different subnets that you will have and the hosts that you are going to have. You will have faster and more reliable connection. With a Router or a HUB the connection will get over worked and you will see the time it takes to do something is that much longer. Always use switches with more then 15 hosts