This is a short guide to getting started with your career as a commander on Terra-Xi's devastating fields of battle. You should get your base up and running, a stable economy, and on your way to find both some friends and some enemies.
Building your base
Once the Resource Center is complete, you should build a Katai Export Facility, which is the foundation of your upcoming economy.
You will now be able to build Katai Extractors (KEs). This is done on the Terra Center, so go there and start building them. In the beginning they take 1 hour to build, though this will increase over time and eventually each one will take 4 hours to build. The price to build a new one also increases.
You can now start building some combat units to protect you from any attacks. This is done on the War Factory. To start out, you can build 50 Striders.
Note that you need energy to power your KEs. Your Command Center provides some minimum energy, but to increase the amount of energy you generate, you need to first build a Solar Plant. This will allow you to build Solar Generators from the Terra Center.
We are now done building the core of our base. The next step is to build on this foundation, and it is highly recommended that your next steps is to build Mech Production Center 2 and research Nuclear Technology.
The first friends you will find are most likely in the country you are located in. Go to the Country Boards and introduce yourself. You cannot attack anybody in your country, so it is rare that your fellow country members are hostile towards you. Of course, it does happen, especially if members of rival organizations find themselves in the same country, but at worst they will simply not defend you.
Another place to find friends is on the community boards, especially in the forums dedicated to organizations. You should definitely try to find yourself an organization, and this can be done on the Org Advertising forum.
Dealing with enemies
Terra-Xi is filled with potential enemies, and you never know when you might meet one. Be wary of giving out too much information about your base. There are some ways to help you deal with any enemies you may have.
First of all, join an organization. This is very helpful, as they can come help you defend against the attackers. Joining an organization also has the added benefit of being a deterrent to potential attackers since they know you will have an easier time getting defense.
Second, know your enemy. If you spend some time on the boards and join the community more actively, you will find out more about your potential enemies and you may even find some friends along the way. You should also use the Enemy Intelligence Center to its fullest, spying on any potential enemy and check for any changes in their WarStrength, number of KEs, credits, and so on.
With that said, you should enjoy the game for what it's worth and have some fun!