While tier 1 units can be strong if heavily upgraded, most successful runs aim to reach tier 5 units like Necromancers, Golems, and Cyclops as quickly as possible.
Spells are your direct way to influence the battle. Chain lightning and poison/fire combos are popular for clearing large groups of weak enemies. Top Hero Builds for Mage & Monsters 2 How to "Beat" Mage and Monsters - Best Upgrade Path Mage And Monsters
Saving gold is vital. You earn 10 coins per 100 saved (up to a certain cap, often 500 gold). Staying above 500 gold until the endgame allows you to build a massive economy for tier 4 and 5 units. While tier 1 units can be strong if