Early Game City Rush: In most maps, the fastest way to gain an economic advantage is to prioritize capturing neutral cities with your Infantry. The more cities you control, the more funds you receive each turn, allowing you to out-produce your opponent. Don't be afraid to build multiple Infantry units early on solely for capturing purposes.
Unit Cost-Effectiveness: Always consider the cost-effectiveness of your units. While Medium Tanks are powerful, they are expensive. Sometimes, two Tanks or a Tank and an Artillery unit can provide more strategic value for a similar cost. Balance your production between cheap, numerous units and expensive, high-impact units based on the current battlefield situation and your CO's strengths.
Repair & Resupply: Damage output in Advance Wars is directly weighted by a unit's current HP; a 1 HP unit deals significantly less damage than a full-strength one. Therefore, repairing units at a captured city or base is essential for maintaining offensive pressure. Beyond keeping units alive, ensure they are resupplied with fuel and ammo. Use APCs to resupply units on the front lines to keep your momentum high without retreating to bases.