Awesome advice, and to add:
Help yourself by adding spire-sets.
They give a ton of scrolls, resources, mana, fragments, population, decent culture, and CCs, so you do not run dry on those when making power expiring buildings. You will get them from the Spire also (both CC, and armorers). For easy tourneys, max out and gather all the knowledge, for harder ones, you want to do 20-25 provinces. I have maxed out barracks for woodelves, five armories building a sixth, level 28 Needles, and level 7 for the other military AW up to Woodelves (Victory Springs is not yet available in woodelves.)
I have the entire chapter except the last SS (and an unresearched optional SS) before AWs, and this week:
I have also a few power buildings (south-west, where I also have forest fabrications). They will be gone by tonight after the Spire opens and I complete it (you can fight it entirely too, all the way to the 3rd floor the last boss, included.)
My city is quite outside the box, I have seven spire sets, and will have eight when remodel upon going to sorcerers maybe this Thursday, when my Needles are level 30 (28), or maybe a few more military AW first.
I have 5 Magic Workshops and a regular one, waiting for the sixth. I craft 100% refill tool spells, I have plenty of CC with spire sets, whole spire, and 10-11th FS collective prize (22 more boosters, 22 more CCs).
Note the troops we needed for this tournament, (15th), and my available squads.
So, with what you have in woodelves is plenty, plenty, plenty. No need to spend a single diamond, maybe to open the doors in the Spire if your birds' tummy is going to empty, so you get the best out of your pet food. But you will get those diamonds back probably anyway.
Zero carter or diplomacy,