Economy (EU2012)

Satellites

Your number one source of income in the game is satellite coverage. Because you get income from satellites at the end of each month and satellite uplinks and satellites have long construction times, you will benefit greatly from some planning to make sure you can launch just before month end, rather than just after. Remember to factor in the engineers and power you'll need and make sure you build generators and workshops with enough lead time. Your satellite links should be your first priority for adjacency bonuses, because an extra satellite is considerably more valuable than +2 power or a workshop rebate. You will need 16 satellites to cover the whole world, so with 4 satellite uplinks and a satellite nexus (or 2 satellite uplinks and 2 satellite nexuses) you will need 4 adjacency bonuses.

While Managing Panic will be your first priority with satellites, fully covering Africa should be a major priority for the 30% increase in global income.

Gray Market

The Gray Market is your second major source of income. While selling things you might need later is a painful decision, it's almost unavoidable to be able to afford to equip your soldiers properly while keeping up with satellite deployment.

Sectoid, Thin Man and Floater corpses are usually good bets in the early game, since you will usually get more. You should stop selling Sectoid corpses around month 3 and Floater corpses around month 4, because you stop seeing those alien types and you may want the corpses for the interceptor consumables. You'll always have a supply of Thin Men from council missions.
While it may be tempting in the first month or two, you should never sell weapon fragments because they're the main limiting factor on research and foundry projects.
While less crucial, it's easy to run out of alloys and elerium to manufacture late game armor, so also avoid selling those if you can.
After researching them, UFO Power Sources can be good things to sell in the early game. UFO Power Sources are mainly used for Firestorms, but interceptors with plasma cannons will suffice until late in the game, and are otherwise only used for Elerium Generators, which are pure luxuries given Thermo Generators can easily fulfil your power needs. UFO Navigation is similar but is used for Satellite Nexuses, which are useful for completing your satellite coverage, so think a little harder before selling them.
If you have the Slingshot DLC, and complete all 3 missions on the first try, you get a massive supply of Elerium, Alloys, and a few Computers, Generators, and two Fusion Reactors upon completion of the third: you can easily sell a good portion of each on the Grey Market, keeping you well funded quite early on, and not be hurting on these resources later.

Council Requests

Once or twice per month a member nation of the Council will ask for XCOM to supply them with certain items.

Occasionally they will ask for a satellite to be placed over their airspace; this must be done through the normal Launch Satellites screen.
More usually they will request items from the Gray Market list or that XCOM can manufacture (Laser rifles, arc throwers, etc). This is the only time that items from the latter category can be sold.
In exchange for the items or satellite, the Council nation will provide XCOM with a single reward similar to those offered for abduction missions. (i.e. the nation will offer one of either scientists, engineers, a veteran soldier or cash).
If cash is offered, it will always be greater than the normal going rate for the items. For items that can be manufactured, the cost will always be high enough that you can make a cash profit by building the items to order, but the cost of components (weapon fragments, alloys, etc) needs to be considered.
In addition to the economic gain, fulfilling these requests improves your score at the end of the month.+
The advice from the section above on general use of the Gray Market also applies here.
If you don't mind save-scumming: loading from at least a little before the request is made, the requested item and reward changes each time you load. Obviously, best done for profit, but also if the item they're asking for isn't something you aren't too keen on giving up, or don't have the resources to make.

Cost avoidance

Only buy or build what you need rather than what you want.

You can manufacture soldier equipment instantly, even just before a mission, so there's no need to stockpile. If you find you need an extra nanofiber vest for your squad setup just back out, manufacture one and select the mission again.
There's little reason to have more than one of each interceptor consumable in your stores. When you use one, manufacture a replacement instantly. Even if you need to use two interceptors in quick succession, you can still easily manufacture another between launches.
Take the time to un-equip items and armor from troops to re-equip them on whoever is going out on the mission. It may take time, but it will save resources in the long-run. Note that injured soldiers who go to the infirmary automatically un-equip all their special gear, but soldiers undergoing Psi Testing do not.

Do I Really Need That?

Some projects are pure luxuries. Soldier recovery time in the Officer Training School is a prime example. It's available early, but it's quite expensive, and you can always swap in a new rookie or squaddie to get some experience. Some Foundry projects are also quite expensive, and worse, they often take Weapon Fragments, which are also required for research projects.

Base Location

There are many different methods to choosing your initial base location. Here are a few factors to consider:

Money: Look at the Funding table.

If you choose to start in the USA, you get §180 each month to start the game, in addition to the Base Funding depending on your chosen difficulty level.

If you start in Africa, you actually get an extra 30% to Nigeria's funding and an extra 30% of the Base Funding thanks to the "All In" bonus; plus, you'll be getting an extra 30% from every other funding source as you expand satellite coverage.

Both are worthy options.

Bonuses: This depends on your play style and gameplan.

If you really want "Future Combat" and "We Have Ways" early in the game, put your base in Asia because it will only take 2 satellites to get S. America vs. 4 satellites if you start in S. America and expand to Asia.

Autopsies and interrogations don't take very long, so "We Have Ways" is probably the one clear-cut choice to not start your base, especially considering you only need 2 satellites to get it through the course of the game.

Panic: Face it, you can't respond to all 3 Abduction missions.

At some point, you're going to get stuck with covering a country with a satellite just to calm them down, whether it's early in the game to keep everyone happy or late in the game to prevent completing the "Doom Tracker".

You can try to keep an extra satellite and uplink slot available for such cases, though not utilizing such a vital resource also weighs on the mind.

Examples

Start in Asia (China) for the "Future Combat" Bonus, then spread to either N. America (Total §330 + "Air & Space") or Africa (Total §325 + "All In"); either way it's only 3 satellites.
- This is a good option if you rely on a short-list of highly perked soldiers for combat.
- The downside is you have to be careful not to waste precious resources on excessive Foundry projects that you may not use in combat very often.
Start in Africa for the "All In" Bonus (because it gives you extra credits no matter what play style or strategy you choose) and then spread to N. America for more credits or Asia for even cheaper deals on Foundry and OTS projects.
- This is a good option if you don't have a particular strategy in mind, or if your strategy is to play it by ear and react to what the game gives you as you progress.
- The downside is that you'll need a couple more satellites to get the other continent bonuses, which takes time, credits, and Uplinks to accomplish, all in the face of ever-increasing panic.