This is the 1998 game by Digital Addiction, not to be confused with the 2011 game Sanctum by Coffee Stain Studios.
Always create a second group of soldiers on your second turn.
Look for spells that will hinder your opponent's movement so you can capture the neutral towns first.
You can protect your soldiers from some spells by using forests as cover.
After playing a few games, look for cards that will let you splash in a third color of mana so you use a wider variety of spells.