Don't think you can solo queue for ops at all, only for regular dungeons. And not even all of regular dungeons; there's some mid 20's ones and I think early 30s that don't have a solo mode yet, like Athiss. They basically made all the ops level 65, though you can join some at level 60 I believe, but they are tuned for full ops groups.
For gearing up, really all you need to do is the daily heroic/dungeon whatever for the crystals, and then buy the slightly lower than max ilvl gear. Shouldn't take too long, and while you are doing that pick a companion that you just dump shitloads of gifts on to get their influence up. Though I don't know how viable "solo" mode 2+ fortresses with companions as nerfed as they currently are. The next patch is supposed to buff them up a bit, because they were absolutely gutted pretty shortly after KotFE release.