1) Wrath of the Liche Queen. Seems EVERY medieval fantasy game has to have one part of the game dealing with undead, I swear! Having trouble getting around this.
No Krypta temples, so Paladins it is! Depending on how fast the enemies hit your base, you might need to recruit a few warriors to hold you until you can get paladins.
I'd probably avoid Wizards so they don't get themselves killed on vampires. Seeing a wizard teleport in and burn a vampire to ashes before it can respond is a glorious sight, and seeing a wizard ever so slowly limp away from a pack of vampires is an amusing sight (fun fact, wizard walk speed is ever so slightly faster than vampire walk speed!), but seeing a wizard walk up to a vampire and commit suicide on the magic reflection is a depressing sight.
2) Tomb of the Dragon King. It's almost like Skyrim except these dragons are less annoying and a bit more dangerous.
3) Slay the Mighty Dragon. May have to do some save-scumming to find where I need to go in this mission and then go from there. That's what I did in "Quest for the Holy Chalice" to find the site of the objective and beat it from an earlier save file.
Something interesting that I saw in a guide: dragons actually have a hard time killing skeletons. Dragons use ranged attacks, and skeletons have an absurdly high ranged evade stat. Priestesses!
I seem to recall that clusters of ballista towers were also handy, but I haven't played either of these maps in quite a while.
Gnomes might be helpful to scurry around and repair your buildings quickly?
4) Legendary Heroes. Found a barrow. Destroyed it. Regretted it. Sounds like I'm supposed to find and destroy them simultaneously but I could use more pointers.
Resign yourself to a heaping helping of awful. This map is going to be a slog and depending on how the barrows spawn it might not even be a feasible win. You don't instantly lose when time runs out, but iirc a permanent earthquake starts and doesn't stop until you either win or lose.
I don't remember much about this map except hating it. Don't make barbarians, because you need your few scouts to actually scout instead of following a barbarian around.
Speaking of awful, Vigil For A Fallen Hero is also going to be awful, though in that map one of the biggest hurdles is keeping your heroes alive. Get healing items and an inn in place pronto, and be generous with reward flags so your heroes can afford to improve their gear. The money more or less comes right back to you anyway.
5) Brashnard's Ultimate Sphere of Destruction. Seriously, I am having Trouble wrapping my head around this one.
I seem to recall that this map was mostly a difficult start, but after you got established you were probably going to win. That's all I recall, unfortunately.
6) The Siege. Looks like interrupting caravans is the way to go but how exactly to go about that?
Avoid recruiting Rogues or Elves, because you'll be up against another sovereign that WILL place reward flags on your stuff. You don't need your own rogues wrecking your guard towers while you watch helplessly. Feel free to make a Rogue Guild, just don't recruit any rogues.
Be wary of his elves and rogues. A lot of the previous advice on warding them off still applies; you need to keep them off your citizens. Be ready to use spells on your heroes when your heroes clash with his heroes; he uses spells to buff his guys sometimes, but I don't recall ever seeing him trying to burn down one of my heroes with offensive spells.
If you can find the locations where caravans spawn and erect several ballista towers each spawn, the towers should take care of the caravans automatically. I've always won by running him out of gold, but it can take a while.
7) Darkness Falls. They're just coming it of the woodwork in a flash!
I seem to recall swarms of shadow beasts being an issue. Don't recruit the slower fragile heroes.
8) The Valley of the Serpents. Trying to save the Bungalows AND destroy those enemy structures? Hoo boy...
Remember that you only need to keep one bungalow alive. Once the elves make a few in your base, then you can surround them with some towers to help. Focus on securing a local bungalow before worrying about attacking the enemy lairs. You don't want to try to secure a distant bungalow because it will strain your resources.
9) Balance of Twilight. Just... weird.
I read somewhere that this map is actually bugged and crashes before completing. When I saw swarms of shadow beasts (was it swarms of shadow beasts?), I didn't bother to try and finish it.
I have yet to touch The Wrath of Krolm, and obviously unlock the other secret quests.
Wrath of Krolm is interesting. You'll be up against a lot of barbarians, and you'll be on the receiving end of Wrath of Krolm spells. The buffs to enemy heroes are no joke. Make sure you either break multiple altars in a very quick fashion, or take time to recover after each altar is broken.
No progress as far as Advanced quests. Blows my mind that I've beaten two Expert quests so far but not the Advanced ones I haven't beaten. :o
Don't get too caught up on whether a particular quest is marked as Advanced or Expert. Some of the Experts are easier than a few of the Advanced. :)