Starting Tactics

What is Doomed Earth?
Doomed Earth is a 12 player diplomatic free for all where players assume control of one of the 12 major powers left on Earth. You must use diplomacy, army management, and most importantly knowledge of the Doomsday weapons at your disposal.The single victory condition in War for Earth requires a single player to control 70% of Earth's population in cities. Once this victory condition is met the "secret found" text popup will announce the end of the game.

Starting Off:
Diplomacy

In the first few minutes of the game the most essential ability is to assess your neighbors skill level. Low level skill players should always be targeted first, their population and resources are more important in your hands than theirs. Allying unskilled players is also discouraged as they most likely will not offer much contribution to your future conflicts with other players. Most countries start off neighboring more than a single country, others, such as Brazil and South Africa are only situated near a single nation, and in the case of Australia totally isolated. Your strategy should fit the geopolitical situation your starting country is in. Nations like Russia, China, and the United States should not be inclined to attack more than one player at the start. This is to discourage fighting two players at once.

Government

The best starting governments should fit your early game needs. Take note that whenever you switch your government its broadcast to the entire lobby.

This can backfire when switching to certain government types that alerts the lobby of your intentions
 * Switching tyranny or anarchy alerts your neighbors that you plan on being aggressive.

Most other governments are neutral and each have their pros and cons, assess your material and income levels and exterior threats before switching.
 * Switching to undead coalition government will alert the world that zombies are incoming.
 * Switching to weak army governments like Medicated populace, Clone Population, or Democracy lets the world know you are focusing on economy instead of expansion.
 * Switching to Terrorism implies you do not plan on expanding early but rather building doomsday weapons to make nightmare scenarios late game.

Being stuck in a bad military government while an army marches into your core can be game ending!

Expanding into Neutral territory

The majority of Earths population in cities at the start of the game is not controlled by any player. Its advisable to take these neutral cities as fast as possible and learn how to deal with the neutral defenders. Most of these cities only have a few infantry defending which can be dealt with easily by a single tank.

The cities that are defended by a bunker or a artillery turret are a bit trickier.

- The neutral units and structures will always prioritize the unit that is closest. In the case of bunkers it's always important to make sure your tanks are in front of your infantry, as bunkers do more damage to light (infantry) and tanks can easily be repaired.

- Artillery turrets are extremely effective against tanks but weak against hoards of infantry. Hence why the opposite is true for taking out turrets. Keep your infantry in front of your tanks and keep moving them closer to the turret so more and more are in range of firing.

Early game unit Composition 

This is up to debate but ideally you want a mix of infantry and tanks at the start. Tanks have good DPS but are expensive and have low health for their cost. The first upgrades you should get are Advanced Infantry then combined arms then improved weapons. Combined arms is the best early game upgrade as it allows your infantry to move as fast as your tanks allowing you to move your army quicker and expand faster than your opponents. Advanced infantry unlocks specialized infantry that perform significantly better than basic infantry.

Early Game Economy

Your first priority should be securing sources of materials. Money comes from population (energy) in your cities and there is little you can do to increase that initially beyond taking cities that aren't under your control. My favorite method of getting an early game surplus of materials is through tree farms and oils. Oils look like black vespene geysers and the most optimal way to harvest them is to put a harvesting depot directly next to the geyser so that they are touching. Harvest using only 1 scv, using more than one doesn't increase harvesting rates.

Tree farms are another great way to get a good early game material income. You are limited to only building 2 tree farms to reduce lag. The optimal setup looks like this:

Key:

F = Tree Farm

M= Material Depot

t = Tree spawn area

Without any harvesting upgrades it takes 5 scvs to harvest 2 tree farms in this setup

With the harvesting upgrade from the civilian research center it takes 4

Added with the harvesting upgrade from the prototype weapons research center it takes 3

Added with Workforce Automation government it only takes 2