GUNBOAT
The gunboat supports your ground troops. It sits off show and possesses an array of attacking abilities. The missiles are useful for eliminating single targets before you deploy troops, or supporting your troops.
The flare is essential for directing troops to where you want them to go. More often than not, you'll be using flares to direct troops out of the range of defensive units.
The medic pack is great to buy your troops a few extra seconds if they are taking heavy fire.
The shock bomb is a great addition when you unlock it. It stuns several buildings at one. Fire to into the middle of a set of defensive weapons, to buy valuable attack time, or combine with flares to sneak by and move out of range.
TROOPS
Riflemen
In sheer numbers, riflemen can take out anything. Combine with flares, shock bombs and medic units to take out defensive buildings, leaving the bad open for them to complete the job.
Heavy
The heavy has high health and can soak up enemy fire, allowing other troops to take out defenses. The big gun in the picture looks great, but in reality they don't do much damage, so they are used best as shields for riflemen or zookas. An army entirely made up of heavies can be focused on the HQ without needing to take out defensive buildings first. It's an expensive strategy though!
Zookas
Zookas provide high damage, but at a cost of low health. They are easily taken out if not covered well by heavies. The combine well with heavies. Lots of players use armies made up of zookas and heavies.
Warrior
Warriors move quickly and when used with smoke screens can sneak through to the HQ quickly and steal a win. Use them with shock bombs to keep the defenses turned off.
Tanks
Tanks are slow moving but are a lot of defensive units that can cause major damage to them. Spread them out and take advantage of their long range fire power. Combine them with medics to keep them healthy. Some defensive units cause double damage to tanks though. They do well against snipers and machine guns.
Medic
Medics will follow troops and keep replenishing their health. Use medics whenever you can. They are will worth the unit space that they take up.
STRATEGIES AND TIPS
Heavy Shield
Using high health units like heavies out in front of riflemen or zookas is a great low level strategy. The heavies will soak up enemy fire and allow you back up units to dish out damage.
Sneak Attack
Look for badly laid out bases that allow the use of flares to direct troops around defensive units just out of their range. This is a great tactic when you are new to the game and don't have shock bombs or some screens. Shock bombs add to this tactic. You can stand I the trees at the back of the map too. This is the most cost effective strategy.
Rushing
Direct warriors to the HQ with the use of flares. You'll need to use shock bombs to make this worthwhile
Check out the videos below for examples of other offensive strategies. Feel free to add comments below with your own tactics.