Power cable for the Router
http://www.andymark.com/product-p/am-3082.htm
NavX Board
http://www.andymark.com/product-p/am-3060a.htm
Enough control systems (roborio, power distribution board, etc.) for 2, maybe 3 robots.
Our teams' schedule this year is:
End of week 3: Test robot (robot on a board) for the Programmers so they can start testing code on a target configuration.
End of week 5: Practice robot (version 1 of the robot)
End of week 6: Competition robot
It is expensive the first year, but in future years, you can cannibalize the Test and Practice robots.