Clearing neutral creatures.

Playing as Haven, I noticed an interesting feature. If there are strong archers around the mines and you don't risk attacking them and stay in your castle, you can buy the Cloud Temple right after the Golems, because the market provides gems, and that's what you need for the Colossus. Life will immediately become easier, while my friend bought Necropolis and was losing – I had Golems, Tubmoks, and Gremlins, plus a couple of Titans (for comparison, he only got dragons after 3 weeks, i.e., +6-8 units of level 7 already gives an advantage).