For your reference.

As for the coupons, I think those should work. Check the resources needed for upgrading the Cathedral and the required building levels when upgrading the Cathedral. Distribute the speed-ups for buildings, troops, and research appropriately. Even as a free-to-play player, when building times get long later on, you can unlock an additional 1-hour construction for 500 diamonds. Use that for Cathedral upgrades, and use the basic construction slots for buildings with shorter completion times or essential buildings needed for Cathedral upgrades. Also, you should save up 10,000 diamonds early on to buy the 30-day VIP, which will shorten construction, research, and troop training times. Joining a guild is absolutely essential. It's best to join a Korean guild, and joining a guild in the top 10 server rankings will give you various benefits. If you can't join a top guild, at least join a guild where many people are actively online. If you join a guild just because it has many members, but they aren't often online, you won't get the benefits of reduced construction and research times.