I agree with boonie.
Try to get a site on Gillis - move to Bat if you need to. Of the other lakes you mention... I can say that the lone site on Virgin still rates as the worst I've ever seen in the BWCA. The site on the south shore of Powell is something of a hidden gem - its certainly nothing spectacular but, IMHO it's the cream of the crop throughout that area between Lil Sag and Gillis - if you want/ need to pull up short of Gillis. Gabi is a beautiful lake with some awesome campsites.

photo of Virgin campsite.