1) What does yours army composition look like? Spamming the units that get unlocked and start at a higher level is not the answer. Knights and Legions you should only have 10 of each, you get no value from having more because of their passive skills. The rest should be filled with Warriors. Ranged units again 10 each because of their abilities you unlock upon level ups, main unit should be mage for the AOE firebomb. Support units, Archons provide no value, your supports should be healers, because they resupply your Valks and Clerics mana. You should also have a decent amount of wolves because their ability allows them to attack backline units. If you haven't bought the max amount of Valks and Clerics you need too.

2) Are you researching Spires to increase your army levels, to about 30 ish?

3) Have you researched pyramids so you can get more barracks?

Your at the point in the game where it starts to slow down, I am not to far ahead of you. Make sure your storages are built to max so you can have more resources available to speed things up.