Running servers in consols...
 

If going to run a bunch of different types of servers on one computer, say 3 games servers and an ftp server, should I start each in a different tty?

That would probably add just a bit more overhead load on your CPU. I'd create a script that will start all the services you want.
Or start each one by hand and put & at the end of each command to get you back to the command prompt.

run them all as daemons? The ftp server too?

This is way off topic, but its a quick question: Is it normal to have 50 percent cpu usage when transfering a file at 100mbps?

If you use the command on the command line and put the & at the end of the command, then it will run in the background, not as a daemon. The ftp server would run as a daemon, but that should be started from one of your init scripts.

That's kind of a hard one to answer. It could be normal, but there are so many variables that can affect it.

Any other optimizations I should know about when running an sftp server on the same box as 3 game servers? I'll probably be running gentoo.

Sorry can't help you there, I've not run game servers before. I would imagine you would have a larger memory requirement to do that though.