Whirlers are upgraded with Halberds in case anyone is wondering. Yeah game is pretty simple and gets repetitive after awhile. A fast forward button would help speed up the monotony.
Fastest way to win if your unique unit is a melee is to send it out followed by 3 spearmen, rinse&repeat. If it's a ranged unit just pick a lane set on auto release and do something else. Save your money to upgrade your unique unit's weapon or armor. Speed is pretty worthless since the game is focused on killing their units so you can charge and keeping your units alive so you don't get charged.