The first thing to do, as any race (what I do) is buy 200 Crystal off the Black Market. At the same time, build a Crystal Extractor and a Cap Ship factory. Build 4 (or 3, depending on which race) Light Frigs and station them near your phase-lanes. Get two Scout frigs and put on auto-explore to get the entire map down.
Build a Colony Cap Ship
TEC: Akkan Battlecruiser
Advent: Progenitor Mothership
Vasari: Jarrasul Evacuator
Upgrade the Colonize ability and make a fighter squadron from it. Form the Light Frigs and the Colny Cap. Find a ripe planet and take it over.
I suggest taking out the Krosov Siege Frig first. Once that's done, take over the planet while the rest of your frigs deal with the last Cobalt. It saves an extra two or so minutes.
Once you have three-four planets, scuttle some un-important buildings on your cap planet you don't need anymore (Cap/Frig Factories, for example) and build them on your border planets for max protection. On your border planets, build 3-7 Defense Turrets with 2-3 Hangars and 1-2 Repair Structures. Remember that every planet is a prime target for the enemy, and keep a constant alert on your planets.
I forgot. ALWAYS KEEP ON THE OFFENSIVE. Don't let up, keep raiding and assaulting their planets. Otherwise, if you say, "I'm just gonna build more ships" WRONG! YOU FAIL!
If you give them enough time (10, maybe 15 minutes) THey will bolster a fleet to rival the Imperial Navy Fleet at Endor! Seriously, keep the pressure on them and they'll run out of ideas. Even experienced players get smashed by Easy AI's if they defend when they could just smash the enemy's remaining defenses.
But, it you defend, just to get a feel for what it's like, stack up on three key ships.
1) LRF (Long-Range Frigates) Have about 20-60 at each planet for an easy win
2) Light Frigates (Cobalts, Disciples and Skirmishers) Have at least 65-80 of these at a planet. If you lose some, quickly rebuild them. THey're like Kamikaze units, but are actually quite effective. If you send a large amount, say, 40 at a Cap Carrier, some actually might survive, which adds experience, because the more that attack, the more will prevail. The Cap will most likely get destroyed, coupled with the LRF's firepower.
3) Anti-Fighter Frigates (Garda Flak Frig, Defense Vessel, Jasurak Sentinel) Have 25-50 of these prepared at all times. They can prevent Carrier Spam (It depends if you're spamming LRF's).
These three classes, while working together, are surprisingly effective at most times and can deal with almost any enemy. But remember, they're just a small defense force to hold the planet long enough until a bigger, better fleet arrives.
Rule No. 1) NEVER MOVE A DEFENSIVE FLEET. I call them "Build and Attack" fleets for their suicidal-type defenses. This includes the defense fleets above.
If you move them, a planet can have drastically reduced defense. If a scout comes along, sees this, and retreats, chances are they're gonna come in. Hard.
Defensive Fleets don't include a normal fleet, such as Caps, Carriers, Cruisers, etc:.
Rule No. 2) Research As Fast As You Can. Researching is your best friend. Use it. But don't use your entire economy on trying to buy Super Weapons. 90% of the time, people (or AI) I play win because of the things and subjects they researched. Combat Researches can be good, but Empire ones are better. Long Range Jumps are your best friend in Multi-Games, cause sitting in the star system you control by yourself isn't very fun either.
Rule No. 3) Never Use Super Weapons UNLESS NEEDED! 95% of the time Super Weapons (Novalith Cannon, Deliverance Engine, Kostura Cannon) are unusful, a waste of your economy, and most of the time get built on border planets.
Really, I see those structures as last resorts. The Kostura can destroy nearby Structures on planets, while the Novalith can tear a planet (or asteroid) apart from across the star system. The Deliverance Engine I think works the best. It automatically spreads your culture deep within the enemy's planets, which could cause rebellions and a chance to rebirth.
Wow. That was a mouthfull. Hope it helps.