Update: we have a slight issue, in that Skr (Green player) went and grabbed an empty castle right in the middle of our area. This castle was mentioned a while ago, and marked on the map but none of us went and grabbed it, which is a slight facepalm moment. The real risk is that Green decides to extend his region to the South by taking over cities here, so please go for a city as soon as you hit level 15. Ask here for help from higher-level players and we'll help by exterminating guards for you, to soften up the defences. That way elite guards will be no problem.
People should speed up making fortified garrisons if you can. Even if you're not level 15 and can't take a city yet, you could help out by getting some recruits together and start working on building fortified garrisons. Definitely level up for a city, but you can work on fortifying the countryside somewhat before that, it's all helpful.
To speed things up, I'd like to try a collaborative experiment. I want to try dropping a castle on top of an existing garrison that belongs to someone else. (78,78) would be the most convenient location. If that works then it would streamline things a lot in securing those blue positions I marked on the map, and I'd be happy to pay for the building materials, if others can manage getting some recruits to guard the castle.
If it's not possible to build on top of someone else's garrison, we'd have to coordinate to be online at the same time, I go build the castle, then you seize it right away and stick some guards in. The minimum level for seizing a castle is probably the same as building one, level 10.