The most challenging maps for you.

If you play on impossible difficulty, it's not that simple. Building Wyverns, in addition to the huge wood cost, requires a lot of gold, which definitely slows down development by a couple of days. But in general, if you play a random Fortress and have a lot of resources on the map, you can build everything up to Wyverns (and even them) and build a Castle. But in general, you need to know how to play with this town, IMHO! :D

At the beginning of the game, you can attack even without Wyverns. It's difficult to play with any town. Is it easy to play with Titans? While you're upgrading Titans, others will conquer the whole world! :) And un-upgraded Titans are not worth much. IMHO
Have you played the "Ready or Not" scenario? I played it on impossible difficulty in 22 days. True, the town had Green Dragons. So, I completed this scenario with a hero, even without a spellbook, I just forgot to buy it, i.e., I didn't use magic at all. And when building the town, I didn't reach either the trees or the dragons. I think there were only 4 initial units from the town in the army, or even 3. The main thing is speed and surprise. When I approached the enemy Fortresses, they didn't even expect me, but were collecting various minerals :) I took the town, strengthened myself, caught up with the enemy army, defeated it :), and went to another opponent. IMHO
Sincerely.

Added 17 minutes ago

It takes an extra 3 days and 17,500 gold to build a treasury, but it will only pay for itself in 11 days.

I remembered. There, the language is sometimes Russian and sometimes English. It's hard to remember. I meant that you should first build a town hall and a city hall, and then a capitol, if possible. Although I always preferred to build a capitol first, then the highest-level troops. The point is, what's the use of a tower where dragons grow if there's nothing to buy them with? And with that money, you can recruit a bunch of slightly weaker troops that will crush any Titan and Dragon. IMHO
Sincerely