Hi…i am a new user here. As per my knowledge you technically only need 1 cable between switches, and use VLAN trunking over that one cable. With thin clients, you probably only need 100 mb between switches.That said, if you ever need more bandwidth than 1 GB, pulling fiber is a great way to go.
If you have enough conduit space to pull pre-terminated fiber, that would be a really inexpensive way to go.