Economy is the basis for everything done is Command & Conquer 3: Kane's Wrath. It's how you buy everything from structures to units to support powers, and having a good economy is necessary to survive into the late game. For a really solid early game economy, it's recommended to go 5-2 (5 Harvesters for 2 Refineries) on the beginning tiberium field (the one that is closest at the start of the game). It doesn't really matter how you get there, just as long as you get there, but it's really recommended that you don't just start off with building two refineries and three extra harvesters, you will want a scouting party to make sure you're not getting rushed. Once You're ready to expand you have two options to expand, each with their pros and cons.
This is simply packing up your starting ConYard, and moving it to the natural expand (the second closest field).
ConYards can take a much bigger pounding, in case the natural or subsequent expands has an enemy ambush.
In the case of an ambush, ConYards can set down and immediately start building defenses or the refineries in the event of no ambush.
ConYards (Except for Scrin's variant) can crush enemy infantry.
Scrin's ConYard travels by means of air, meaning most ground units can't touch it.
Larger Build Radius than expansion vehicle.
If you don't have any cranes, or other ConYards, you won't be able to build anything until after you unpack at the field
If you lose your main ConYard, without any cranes or other ConYards, you won't be able to build any structures until you build another.
If lost, ConYards are expensive to replace.
ConYards move very slowly.
Expansion Vehicle Expanding
As it states using your factions expansion vehicle (Emissary for Nod, Surveyor for GDI, Explorer for Scrin) and expanding with it.
Inexpensive if lost.
While it is expanding, you can build refineries and defenses.
Faster than ConYard.
Doesn't unpack immediately.
Smaller Build Radius than the ConYard
Now after the first base, it isn't necessary to keep the 5-2 going for every field, because if you did try this, you're harvesters would be getting destroyed way too easily, and your income would be ruined. What you should do, is for every tiberium field, have at least one refinery, and depending on the size of the field, dictate a certain amount of harvesters to it (e.g., on a tiberium field that is almost depleted, keep only one harvester there, and for a newly acquired/full tiberium field, move the majority of your harvesters there.
Never build Tiberium Silos:
If you have so much money reserved that you need a silo, you're doing it wrong, and start spending that money on units.
Never Have a Harvester to Refinery Ratio of 1:1:
You should always have at least one more harvester than refineries, that way if you lose one, you won't have a useless refinery.
Always Monitor Your Harvesters:
I know in the heat of an epic battle your harvesters might seem the least important, but if you find yourself with a break in the action, make sure your harvesters aren't bugging out, or worst of all, trying to do long range leeching off your ally or, even worse, your enemy's field.
Always Try to Snipe Your Enemies Harvesters:
Especially in the early game, if you can manage a couple of attack bikes, pit bulls, or seekers behind your enemies base, try to snipe a few harvesters. This will stop their economy growth exponentially, and, if you can snipe enough, even give you the lead for the rest of the game.