One of the best armies that I have found is ten Samurai and the rest Knights (15). Excellent game, One of the best thing I like about it is that it is simple! It has no flashy graphics, no amazing special effects, and still it is an amazing game.
One thing this game does well is making the AI on the towers fairly smart. For example, the poison tower won't shoot at an already poisoned zombie if there are others within range. Most tower defense games don't make their towers do that.
I don't know if you can change the icons, but I played as Arigal, the top left one, and it shows that I have 0 swords when I start out producing spears...
If you can't get past a level, start by building one row of Coprocessors and Moneymakers each. Then get two to three rows of cannons. Get another row of Moneymakers (add Coprocessors as needed.) Then just keep repairing all turrets as any of them get damaged. You should still have plenty of money in between attacks to send plenty of attacks yourself.
Amazing game, I started as an Archer. I'm now a level 24 or 25, and the only problem I've had so far is a Unique Venom at the beginning, took me over 5 hours just to get to a high enough level to beat that, but I haven't had any problems after that. I give it a 5/5.
My mouse quit working for me on this game quite often... It gets pretty annoying when there are about a hundred bullets flying at you, and your mouse stops working.
To get a farther flight, after you get the rudders, throw the plane. Then, let the plane get close to the ground and use the rudders to stay close to the ground. By doing this, you get many of the spinner things.
For the first time players, do Hakkaido. Also, the best combination for armies that I've found is shields and knights early on, then samurai and wizards near the end.(Also click on the hold button under your armies to let them move up and down to attack all enemies.)