First off, I'm not a big believer in set "strategies" for Sins of a solar empire. In even the most basic strategy game I have a history with, chess, there is no set piece of moves that will lead you to victory over your opponent. You must adapt to your opponents moves. Still, even in chess, there are a few basic "opening moves".
The Generic opening!
All openings are the same for each civ in the beginning. Where they differ is where I will make seperate sections.
Once the game starts, build a capital ship factory first thing. Then send your other fabricator to build the crystal extractor, and cue up the other 2 metal extractors so that the fabricators always are either building or in transit to build. No time is wasted this way. While those are building, sell 100 metal and buy 100 crystal. Then upgrade the terran infrastructure of your homeworld to the 4th level (the sooner you start this, the sooner it pays off, so be quick about it!). After that, depending on map size, cue either 2 or more scouts (more scouts for better scouting. The sooner you find those worlds near you that are big payoffs, like lightly guarded terrans, the sooner you can take them over. Finding neutrals is also key in Sins). Cue your capital ship before the factory is done being built so that you waste no time in getting your first capital ship out and into the fight. Now you've used all of your starting income to set your fledgling empire on the right track as fast as possible.
Opening move for Vasari- The assailant is probably vasari's greatest unit. It's tier 1, does a hefty amount of damage, and does that damage at a longer range than just about any other ship in the game. It uses 1 less fleet supply than the basic skirmisher, and costs only a few resources more. This sounds like our perfect spam unit in the early game. Being tier 1 means that vasari can have them out quicker than any other civilization can have their LRMs, and their research and building requirements are cheaper, which means more early on!
After the generic opening, your capital ship should be rolling out shortly. Make sure to cue up the Evacuator, the single greatest vasari capital ship in the game! Not only does it colonize planets, but it helps melt enemy cap ships like butter with it's nanites. By the time your cap ship is done being built, you should have the areas around you scouted, particularly an asteroid near you that is very lightly defended. This should be your first target, as the cost vs return is balanced high in your favor. Send your capital ship there as soon as it's built, selecting your strikecraft type and colonize as your special ability.
As soon as the roid is captured, start making all the extractors and upgrading infrastructure. If the extractor isn't making you money, it's losing you money in opportunity cost! Get it productive as soon as possible. Make a military lab on your homeworld and start researching the assailant research. These early assailants will help you expand quickly, thus building your empire.
(A note about vasari scouts- If the map size is large, then make more than usual, because vasari scouts can capture neutral extractors across the map. This single ability makes the vasari scout one of the most powerful units in the game. With a few neutrals, you will have not only the resources you need to build and expand, but to sell off for more credits, thus generating an income of it's own).
Opening move for Advent- Same as Vasari, you will want to take your asteroid as quick as possible and cue up the extractors, but for Advent you'll be cueing up the most useful capital ship in Sins, the Mothership. The mothership not only colonizes planets (make this your first ability), but also regenerates the shields of all your ships in a certain radius, and helps spread damage to all enemy ships in a certain radius. These two abilities make the Mothership the most helpful support ship in the game, by a long shot.
Once your roid is captured, start making hostility research facilities. Once these are done, research Illuminators, the best LRF in the game. As soon as the research is done, start pumping them out like mad and take over near planets that would help build your empire (terrans and deserts are top priority as they require no overhead research, ices are second, volcs third).
Opening move for TEC- TEC is a little weird. See, TEC's colonizer capital ship just sucks. No no, not drain planet here, that would be awesome, we're talking about hardly any useful abilities compared to the vasari or advent colonizers. So, you're forced to experiment a little.
If your opponent is really close, build a Sova carrier capital ship, and cue a colonizer frigate from your frigate factory. Send the sova not to the roid, but straight to your opponents homeworld, and cue up three cobalts. Send these cobalts to dispatch your asteroid's defenders while building scouts and cobalts back home, and then colonize with the colony frigate. Then send the cobalts to your opponents homeworld with your cap ship, along with all the other ships you have made. Use the scouts to kill builder drones and the cobalts to attack enemy ships. The scouts can help with the enemy ships once the builders are dead.
Or, make a Marza. A lot of people suggest a Kol for it's pure fighter characteristics, but the truth of the matter is that the Kol loses it's bonuses quickly in the mid game. The Marza though serves as a great planet bomber for the rest of the game, easily reducing enemy worlds. Use the marza to help clear the roid while making two military labs (make sure to save enough for the roid upgrades though!). After the military labs are built, start making a few LRM ships to help clear more planets. Then, either make a ton of LRMs, or make more labs and build Kodiaks, the ultimate TEC cruiser.
To help consolidate my posts, here's my Golden Tips for Sins-
All in all, I think new players should move away from the idea of a dynamic strategy. There is no good "strategy", only effective tips and pointers to live by, coupled with game knowledge. What is the point of a "strategy" build order that you follow if your opponent ends up producing only ships that counter your strategy? How effective were you?
Let me refer to some classic historical examples to reinforce my point, mainly Erwin Rommel. His victories were attributed not to superior numerical force, but to adapting to his enemy's strategy and incessently probing for a weakness. Once one was found, he would exploit it 100% until victory. This is the sort of mindset that will make a good player at Sins, not one who has mastered a build order.
The Golden Tips:
1) A saved credit is a wasted credit- This is the king of all tips, and one that even good players need to adhere to more often. Think of each credit stored as an opportunity cost. Those credits, sitting in your "bank", could be dealing damage to the enemy, earning you more credits, or making your empire more powerful through ship upgrades. Leaving them in your account does none of the above, so what's the point in saving them? You shouldn't be saving up for a second cap, as one isn't practical until the point in the game where you have so many resources you should have won already.
2) Scout often, and thoroughly- A lot of players whine about how overpowered RA is, or how illums are unbeatable. Why are both of these things so hard to combat? Because of your own incompetence, not always because of your opponents superiority! Ask any player online whether you should scout often or not, and they will all agree that you should, but even good players are lazy about this. Here's a tip- At the start of the game, build as many scouts as you have lanes moving to other planets, and then depending on map size and race, build more. If it's a large map, or you're vasari and there are neutral extractors, you should obviously have more scouts than the first 2 or 3. Why? Because knowledge is the key ingredient to winning a game.
Think about how easy the game would be if you could see everything your opponent was doing through his ship vision. If he was going RA, you would know because you'd see him making a lot of imperial labs! If he was making a hostility early, you know he's going for illums as there is really nothing else advent has early that are worth building that require hostilities! So when you see these things, you know how to react. "Oh crap, imperial labs like crazy, we need to go hit this guy who's dumping all of his resources into 25 minutes worth of research and civic building to get his RA." "Oh, he's making a hostility, I better make 4-5 scouts and go kill his builders so that he can't make anymore and he's a sitting duck!". Plus, scouts do anti-light armor damage. 3 scouts will kill 1 illum, and have other obvious uses as well (plus are more cost effective. They require no buildings or research).
3) Adapt to your enemy- With proper scouting and a basic understanding of game mechanics, you can build ships according to your enemy's fleet. This is what ultimately leads to victory. If your enemy has a bunch of carriers, why wait to find out the hard way? Scout, and build flak! Etc Etc.