Get Cat5e cabling at least as it would be be best for gigabit ethernet and speeds between your computers. For the connection from modem to router CAT5 is fine as the speeds won't get high enough to get 5e. Price is pretty cheap online, you'll get totally robbed for cable prices in regular stores though, even bargain places like WalMart have a large markup.
Any switch with 1gb ports is fine. Try TP-LINK TL-SG1008D, top rating on www.newegg.com, had 8 ports so you can hook everything up to that with room for more.