I am a good Starcraft 2 player (used to be in the top 1% of players worldwide before I started playing Diablo 3) and I also played SC1, Star Wars Rebellion and Rise of Nations, but Sins Rebellion is my first Sins game.
Excellent, someone else who has played all these games. Not that I check often, but I rarely run into people that have.
1) I picked TEC loyalist as the first race I’d try, although I am opened to suggestions if something else seems better, I heard this race is good for doing an economic boom, although at this stage I have no idea why, so why is this race good ? What's the biggest advantages of the other races?
TEC have the best economy as a race [I believe], with a lot of that strength coming from Trade ports, and their tier 8 tech 'Pervasive Economy' [I think that's the one anyway]. I don't believe it varies too much between Rebels and Loyalists in this regard.
Strengths of each race?
TEC Loyalists have Dual Fortresses or W/E its called - which allows them to place 2 Starbases on each planet as opposed to one. In addition they get Novalith Cannons 2 tiers early, and get them for a lower cost in both resources and tactical slots if I remember correctly. They also have techs that add additional armour and firepower to any of their ships fighting in their own gravity well. Their Titan, the Ankylon, is ok, and good at fleet support. Its shield ability and Inspire and Impare can help your fleet to win, though I've seen it ranked as one of the weaker Titans in game [Can't argue, though I'm not sure how it scales with a fleet].
TEC Rebels have Truce Among Rogues, which makes all Planet Militia and Pirates neutral towards them. This allows them to rapidly expand and makes them immune to pirate raids - indeed sending a pirate raid against a TEC Rebel with the tech actually helps them defend their planet. They also have the ability to call in pirates from Broadcast centres, though I haven't experimented with that ability so I'm not entirely sure how it works. Their Titan, the Ragnarov, is great for single target DPS. It kills things fast, and 1 on 1 I think it wins against most Titans [Not sure if all, I haven't fully tested]. Their Corvettes are also IMO quite decent, reducing the armour of enemy ships.
Advent Rebels have Wail of the Sacrificed, which allows them to sacrifice 1 planet to deal massive damage to all enemies on adjacent planets pretty much without warning. Seriously good ability, if costly. I'm not entirely sure of their other useful techs, as I haven't played that much as them, however their Titan, the Eradica, is quite powerful. A large number of targets, fairly decent DPS, nigh on unkillable if it has a supporting fleet and an AOE attack that can devastate Frigates and Cruisers. Its ult is underpowered, but only if you're facing an enemy who knows what it is and will just run from it. If you're facing someone with no idea what it does, the Ult will slaughter them.
Advent Loyalists... Aren't really to great from memory. They have Cowards Submission, a tech which causes enemy ships leaving a gravity well owned by the Advent Loyalist to have a chance to convert to the control of the Advent Loyalist. They also gain additional buffs in their own culture, though culture is kinda bleh in Sins. Their Titan is, IMO, one of the weaker. Its abilities are alright, but I don't think there's anything I'd really recommend it for, someone correct me if I'm wrong.
Vasari Loyalists are possibly the most OP race around right now. They are able to research a chain of technologies that allows their Capital Ships to give them Credit income and act as up to 2 Research centres of each type, as well as allowing them to continue playing without any planets so long as their Titan is alive, and allowing them to scuttle their planets to receive a massive boost to Credits, metal and crystal. This allows them to get an end game fleet in under an hour if played well, and not have any planets for the enemy to target. Their Titan is alright, though a little weak until level 6. At level 6 it unlocks an ability known as "The Maw", which allows it to consume all enemy Frigates and Cruisers infront of it for a certain distance, killing them and turning them into Credits, Metal and Crystal for the Vasari Loyalist player.
Vasari Rebels are also immensely OP. They have the ability to research a technology that lets their Starbases perform Phase jumps, allowing them to basically field 2 Titans in every battle, with an infinite number of spares backed up each planet, ready to jump forward as needed. Their Titan is also almost impervious to Frigates and Cruisers - it has, thankfully, been nerfed to limit the maximum amount of hull regenerated from memory, however it has an ability that drains health from all nearby ships and repairs the Titan for an amount proportional to the number of enemy ships nearby for a period of time. The more ships you send against it, the more it heals.
2) Which capital ship do you build first?
Generally Colony. Makes for faster early expansion, though if you are rushing a Carrier is the way to go - they beat the Battleships 1 on 1 and can dish out some decent DPS thanks to their Squadrons, and their abilities range from deploying missile turrets to repairing allied ships, dependent on the Race.
3) I guess building a good economy should be my first priority: which researches do you do first?
Depends. Rushing I'll generally pump out LRMs, Corvettes and Flak quickly, put points into Hull techs, then push forward with whatever I can muster to slow enemy expansion. Going for economy I'll unlock LRMs, Corvettes and Flak, then go Civic to unlock Ice and Volcanic planets for colonisation as well as trade ports. If I'm turtling - which generally I think you should try to avoid - Repair bays and Starbases are what I rush for, whilst still getting LRM, Corvette and Flak frigates.
4) How fast do you colonize? As often as militarily possible to kill the ships that are waiting for you on the new planet or its there an optimal economic method?
Far as I know as fast as you can. Get 1 Colony Capital ASAP and send it to one planet, and get 2 Light Frigates and 1 Colony Frigate and send them to the nearest Asteroid. Keep pushing out as fast as you can until you need to defend - but keep building up some military so you can defend unless you are in an Eco position [Only Allies around you, no enemies].
5) Which “secondary buildings” (like trade post, broadcast center, refinery) do you do first? In what order do you do the other ones ?
Trade ports easily. Refineries aren't worth the logistics slots IMO, and broadcast centres you only put out when you need them - to stop enemy culture or when you unlock abilities like Wail of the Sacrificed that require Broadcast centres to use.
6) What’s the best method to kill pirates? What’s the most popular multiplayer setting: pirates or no pirates? (I want to get used to the most popular setting, even if for now I’m playing 1v1 against the AI)
No Pirates. Trade ports work well for killing them [With some planetary defences OFC], though I generally just put down 2 Repair Bays, 3 Gauss cannons and 2 Hangars on any planet that will get hit heavily, and 1 Repair bay 3 Gauss cannons on anything that will get hit lightly, and they'll hold the line for a good half hour or so until your fleet gets there.
7) An hour into the game I had like 20k credits and a few thousands metal, but very little crystal (like 100 because I keep spending crystal). What am I supposed to do to spend my credits and metal? Only trade all of it for crystal?
Well, Light Frigates don't cost Crystal, so you could pump them out, but otherwise yeah - just buy more crystal and use that.
8) Please tell me other tips for a new guy to Sins in general and Sins Rebellion more specifically.
I'll leave this, and correcting any mistakes I've made, to those far more experienced than I am, such as Selucia.