Tactics

Short Game Tactics
In the short games, all sides are going to play out equally. The best tactics are to put in just enough research to give you ship options to counter your oppositions defenses. The tank rush, when you send in dozens of ships in early and often to harass your opponent is by far the best tactic. Pester them enough and they'll start wasting resources on defending against it rather then attacking you. While they're busy with that, you can expand your empire and in doing so, increase your resources and ship production capacity. No real strategy is required since the short game is decided by who makes the mistake of trying to do too much.

Medium Game Tactics
Medium games are similar to short games in the sense it's easy to harass your opponent. The difference is that you also have to consider doing more then just some basic researching, and you actually need to put some thought into defending your planets and holding your ground. You need to start using strategy with your attacks, otherwise you're just wasting ships and resources.

Long Game Tactics
When playing a side you have to play to their strengths. Most people just build economies and duke it out with ships. In a short game, that tactic works equally well for all sides, however, in the long game, your tactic needs to change. This is where people not playing as the TEC tend to start thinking things are unbalanced. In reality, they're not adjusting like they're supposed to. In the long game the TEC can throw numbers at you. They can pull in the funds and put out the ships. They play the numbers game and they do it well. You're not going to do well against a fleet that can bring in more guns then you every time there's a conflict. Trying to outnumber them is a poor strategy that usually results in you losing your fleet. In the long game, the Vasari side basically has more efficient construction and resource saving techniques which saves them from blowing out their funds quickly. They also have the ability to get ships in behind your front lines quickly via phase nodes. Just try defending your planets when the Vasari are using their nodes to gain access at two, three, four, even five different points... They're betting it's going to take you awhile to get there and they can just use the node to return home or harass a different part of your empire once they've got you pulling your fleet back. They basically force you to waste money by maintaining a solid defense throughout your empire and rebuilding everything you've lost. In the long game, the Advent can wage a devastating propaganda war and hold out almost indefinitely on defense. Their biggest strength is the ability to spread their culture, which in turn gives them the benefit of intel, advanced preparation, and attacking without a fleet. No other race get's to see the enemies planets without sending a ship there first. The Advent does it two ways. Via Revelation Battlecruiser's Clairvoyance ability, or by culture. If Advent culture is touching your planet, they can see what you're doing there and prepare to do something about it. No race is ever going to take over an Advent planet without sending a fleet there, whereas, if the Advent puts up a couple broadcast centers a jump away from your planet, then you need to get off your ass and get rid of them or you will lose a few of yours. The less planets you have means the more they have.

If you're going to play a good long game, think about your style of play. If you like to sit back and turtle and research and you don't like to send your fleet very far away from home. You should play as Advent. If you like to tank rush and engage in random skirmishes everywhere, then you should play as the TEC. If you like to build up a fleet and make devastating strikes where you think it's going to hurt the most, then you should play as Vasari.