To summarize, the strategy is based on getting lots and lots of gold by using the doubling property of the robbery spell, so gold is points and mana is gold, hence the more damage is done with the "wizards pal" weapon (which generates 50% mana), the more points you will get. The above steps are the most efficient method to harness the robbery spell that I could think of.
Strategy to get +500.000 points.
1) Complete all levels
2) 10 skill on: Mana, Ice, Treasure, 9 skill points on Gold and 6 on Damage
3) Need in Spell Book: Robbery, Souls and Teleport
4) Go back to Winding Road
5) Build 2 archers for first wave and hit Robbery 3 times
6) Use money for more archers in the back (all archers at the back of the map)
7) Use mana when it reaches 750 at a time you are going to kill lots to get more souls (soul spell)
8) Use souls to ASAP get mages with both tribal threads and wizards pal (50% mana) - place all wizards at the front of the first bottleneck (where the two paths merge).
9) When you have 6 mages use the mana they generate to use the robbery spell (7-9 times per round), if enemies get passed your wizards (which must be in front) use teleport to ensure that almost all damage comes from your wizards,
 "Little Protectors"){kind=icon}