Basically, the main skills are:
Battle - Pretty much 100% combat focused. I'd recommend having some points in this if you plan on fighting.
Empire - Building up and managing the empire. Includes a lot of "tech abilities" which only one person needs to have so it'd be nice if someone would get this to 35 and grab City lights.
High Sorcery - Utility, damage and enchantment. The only skillset that can enchant items and improve them massively. Their utility focuses a lot on empire building (summon materials is EXCELLENT).
Natural Magic - Healing, combat and utility. The only real "heal other" skills, it also has buffs and utility. Can use it to fly etc.
Stealth - Sneaky sneak. Name says it all really. Can also do TF2 spy-ish crap like disguise yourself as an NPC and break into locked houses.
Survival - Gathering, wilderness survival, utility. Useful for combat due to the stamina buff in it, but it's mainly useful for people who want to be herbalists or actually go anywhere. It has "navigation" at 5 and "ride" at 25~. Pretty much necessary for those two reasons. Wouldn't recommend using your daily skill ups to increase it since it's so easy to increase anyway.
Trade - Crafting, crafting and crafting. This is THE craft skill. I recommend maybe one or two more people in here, regardless.
Vampire - Combat buffs, I think? I don't have that much of an idea. We've got enough of these, in my opinion.
Anyway, I was thinking about expansion, and I came up with this idea:
Essentially, we send people to random obscure parts of the map, I promote them, they found a city, my high sorcerer teleports in on that city location and builds a portal. We dismantle the city (so it doesn't use city points, which are the most precious thing in the game) and then we have a permanent link to a distant part of the world.