http://www.youtube.com/watch?v=Z2c9ra9xALc
Well I finished it and I must say it's an extremely awesome game. I salute you if you finish this game. It takes ALOT of planning and patience. It's kind of like a side scrolling RTS, it's a pretty rare genre, for me at least...
Some strategies I came up with:
Shieldmen don't seem that great but they are awesome! If you put a shieldman next to a group of enemies you can bring in a set of archers behind him and crush hundreds of bad guys (this is really important when you fight the green guys in high levels)
Don't try to kill thing with your barrel guys they are pretty much just for blowing doors open and setting fires.
At high levels you may build a platform too far from a ledge, this can be a major problem. Fortunately your structures are all wooden and barrel guys will make short work of them, so you can rebuild.
The white wizard's shield spell makes your guys temporarily invincible, this is great for having someone fall a long distance. You can use it for fighting but I find that the strength spell is usually better.
As far as I can tell the gold is only used as like a scoring mechanism, you can't buy more guys with it or anything.