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If the map isn't hopelessly resource-scarce, I quite often build Ifrits in the first week, about 200%.
You don't need that many resources; for example, compare:
1) how much wood you need to build Riders – 35,
2) how many resources you need to build Unicorns – 15 wood + 10 crystals + 10 gems.
Try gathering and building them. And sometimes it works.
Ifrits are probably the easiest of all level 6 creatures to build.
In the second week, you buy 4 Ifrits (or 5, if you've also built a Stronghold),
gather meat (Imps + Gogs), and easily clear the entire territory,
and by the end of the second week, you manage to build a Castle, Dogs, and Demons (possibly Broodlings).
At the beginning of the third week, you have a Capitol + Warehouse; by the end of the week, you have Devils.
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For example, yesterday we played on a resource-scarce map.
And on the 7th day of the second week, the following situation arose:
we had built a Town Hall + Stronghold + the first 4 levels of monsters.
We faced a difficult choice:
build Ifrits so that we would have 5 of them on the 1st day of the third week,
or build a Castle (so as not to have to wait another week for the Capitol).
On the advice of my opponent (Ewgeniy ;)), I built Ifrits,
although I was leaning towards building a Castle, since there was almost no money on the map.
And I didn't regret listening to him:
by using the 5 Ifrits I bought on the 2nd day to defeat
15 Diamond Golems, I gained access to a rich territory, and as a result,
I managed to build a Castle, a Capitol, and Devils this week.
Conclusion: if I had built a Castle on the 7th day, I would have spent another 5 days in the Castle waiting for the Capitol,
then I would have built Ifrits (but it would have been too late for Devils),
I wouldn't have leveled up my hero in that time, and I wouldn't have discovered a new respawn point or Castle.