It depend on a number of factors. Here are 3 factors I keep in mind when I design my circuits:
-Age of the participants
-Level of intensity I want to establish for the class
-Participant’s fitness goals (for example there is a difference between a tactical operation group vs. a group of clients who just want to get in shape and lose a few pounds)
In my opinion and without knowing any of this information about your group, I would consider a rest:work ratio of 1:1 (or even less rest between stations) for a more advance fitness level of participants to 2:1 for a less fit group. As for the time spend in each station, again this is up to you and the intensity you want to establish for your program. You will get different answers from everyone and it will interesting to see what others think.
I hope this helps.