2. Buy all these items for them:
Banner of the Fallen - Item - World of Warcraft
Captured Insignia - Item - World of Warcraft
Imbued Crystal - Item - World of Warcraft
Monstrous Egg - Item - World of Warcraft
Mysterious Grimoire - Item - World of Warcraft
3. Turn in all these quests on darkmoon
4. Get 75 Darkmoon Prize Ticket (and you can do some dailys for more tickets)
5. Buy what you want, e.g. trasmog for sell it on ah, mounts, pets etc.
Some quest items have too much price now, when darkmoon is active, so you can wait and buy them while event is not active for lower prices and turn in in next dakrmoon.