I want to close all 60 allowed gates...

[IDigWeeds]

...but cannot find anymore to close. I have already closed 50. I am currently at the stage of the main quest where the prince has asked me to talk to the head of Bruma in Bruma's church. I don't want to do that if it means I can't close anymore gates. How can I find more open gates?

[LeftyScaevola]

Selection of the 50 'random' gates is random so you have to find.  At the USEP you can generate a map of possible locations, but will just show you they are all other.  you just have to search for them.  If you have not searched, Blackwood try there a surprising number of them pop up there.

[IDigWeeds]

I have been wandering what seems to be everywhere.  I used the map at UESP, but they simply aren't open when I get there.  I'm thinking that I must not have completed some required activity to open more gates.