Don't build defense structures unless really necessary, they are just wastes of money. Only build them to support the 1-2 chokepoint planets where you have a starbase to kill ai ships that will never pass that planet.

Turn off pirates, online only the minority plays with them, anyway having a tradeport and a starbase is more than enough to deal with the biggest raid (assuming you are not playing the crazy Diplomacy pirates, but it would be another reason to turn them off).

Overextension? Where? get as many planets as you can and build fleets to defend. You can be overextended when you have 40 planets or such.. Get starbases for defense against AI or try to launch an attack if you have more ships than your human opponent, attack is always better than defense against humans, there has never been an issue when someone defended the other one into oblivion if you know what I mean. Attack is always necessary, and it requires a big fleet (counter attack where TEC Loyalist has huge problems late game).

And I tell you what noobs do completely wrong online, they think a Titan, 2 capital ships, and maybe 20 frigates are a big fleet-> LOL where? a big fleet is like 50 frigates, some corvettes, titan, capital ship (but not more than 1-2 capital not to drain xp from titan) and maybe carrier cruisers having bunch of strike craft.

If you want to go online, forget TEC Loyalist, their Titan is too bad for beginners as it completely lacks attack purposes, and stands no chance against any other Titan and fleet. TL can play good, but I only saw experts do that, probably better to start with TEC Rebel mainly for the Truce amongst rogues and the awesome Titan, and for the reason it can do attack well, not like the loyalist brother.

2nd cap? what you would like to. It is fun to try what works and what not, and it is not fun always obeying what others say. OK I can recommend some shis for that. Dunov is good for draining antimatter. SOVA can provide good air support and free missile turrets. Marza has huge frontal firepower and if it gets level6... Consider building it 1st and get Missile barrage fast, you almost won the game by that. Corsev is good, but you can live without it. KOL is great ship, but empties antimatter reserves too early to be useful, but the flak burst can help against huge masses of strike craft. Second Akkan, not good strategy, maybe only for interrupting the phase jump preparations of escaping wounded capital ships.

Slow pace? Online almost everyone plays the fastest settings and only some play fast, so maybe try playing them if you really want to try online

For Vasari they are huge, since they move and can deploy them early. But even for TEC and Advent sometimes you need to buy time to send your fleet to attack somewhere else, or just to build up. Here Starbases can be used well, but you should not be building many, and you should assume your starbase will be lost eventually without support from your fleet. In other words, learn to use them but do so conservatively, and realize you never win any game due to defenses alone.

It's not bad, but the current fasionable thing is to start with a Marza just to get Missile Barrage. And if you're in the Eco or suicide slot I'd say the Akkan is always a better choice.

If you are eco, hell yes. Just get Corvettes and throw 4 civic labs and rush it. You'll need to get the feed tech that's a prerequisite for it in Eco anyways. Only downside of it is that you can't use the pirate base to level up your titan, but compared to faster (and easier) expansion, I say always get it.

I've also gotten it in Suicide slot before I lost my homeworld, as it works even without Civic labs, and lets you run to the best planets while the militia will still slow the enemy down. Not sure if that is a great strategy though.

Frontline it's debatable, but you'll probably need to fleet up before you can get the research done.

Is it possible in suicide spot to survive? Maybe go marza or Kol, spam frigs, and try to hang on until a frontliner breaks through? 

Also, if Im eco, what is my goal exactly? Feed resources to allies or support them on the FL. 

What if the map is a 4v4 or a 5v5 and theres no suicide spots, just 2 frontliners?