N00b, need help!

DL, DA, or TA?  What difficulty level? 

You might play some sandbox games first.  If you have trouble there, tell us how big a galaxy, what galaxy settings, how many AIs, how many minor races, etc.

There are some tutorials out there.  Hopefully, someone will provide some links.

Campaigns are not for noobsor even decent players, IMO. The few times that I have tried a campaign, I have been largely unsuccessful. I strongly suggest you play a sandbox game - the "New Game" button or the "Metaverse" button.

Don't lose faith in the game because it is a great game and you will lose out on it. Try a normal campaign game and tell us what problems are you facing. Or what your doubts are. In the meantime, you can find a lot of game related information on the GalCiv 2 wiki:

https://www.galciv.wikia.com/wiki/Galactic_Civilizations_Wiki

What's DL, DA or TA?

I play the campaign, with the humans, normal difficulty, small universe. I only have two oponents, but they beat the crap out of me...

I've already read everything there was to read. I focus my research on improving my ships, but the other guys are too strong! What do i have to do, so that i can at least have a fighting chance. I mean, i may be a noob, but i colonize almost all the planets, my enemies keep only 4, while i get 9. I have more production power, earn more money, build more ships, do more research... I mean, that should do it, right? But i attack using 6 ships, and they beat me with just one... A civilization with just a planet, class 2, can beat me with a single ship... I must be doing something  really wrong, or this game just plain sucks...

DL is the original game - Dread Lords.

DA is the first expansion - Dark Avatar.

TA is the last expansion - Twilight of the Arnor.

Since you didn't know what these meant, I daresay you can't have read everything :p

The only reason that you can lose like that is because of the tech difference. You are possibly up against the dread lords, who are insanely powerful - they took out my 14B planets with just a 1B troop transport.

I don't know how to win in the campaigns; I suck at them, quite frankly. And I don't like them. I strongly suggest that you play a few normal games (ie non-campaign games, prefereably Metaverse games so that you can't try anything "illegal"). Hopefully, you will like them. Certainly you won't find the AI killing your fleets with one single ship! After that, if you wish you can try out the campaigns again. I have not felt the urge to do so yet

If you are fighting against the Dread Lords (in GalCiv2 DL), then you have to be fast - fast in taking over their planet. That´s the best you can do. There´s usually no way of defeating them once their homeworld is built-up and they produe +200 ATT ships. Because the Dread Lords starts with the whole Techtree already rersearched (like in the 'Battle of the Gods'-Szenario) and the only thing that keeps them from getting a good start is that their planets only have like ~0.1% population than yours (and anyone elses).

And if you know already where their planet is, it´s easy. Take Constructors/filled Colony Ships/Scouts immediately to their planet, en route research 'Planetary Invasion/Bombardement' - create some colonies/starbases (so you don´t have deal with the range-issue) and once you reached their world and the research is done, create a StarBase, transform/update your Colony Ships to Troop Transports (and the Scouts to Star Fury's if the Dread Lord planet is guarded...) and then "Cry Havoc" and storm onwards!

I´d forcus all on researching the necessary techs, then lease-buy your invasive force - and once the DL are out of the game you can finish the rest in normal style.

However, the possibility is there that you´ll come too late - and the DL have built a strong warship already in planetary orbit. Then, well, good luck...

Go back to a save game just before one of those space battles that you lost.  Click on the enemy ship or fleet.  Compare the enemy attack factor, defense factor, and hitpoints to the ship/fleet of yours.  Compare the enemy attack weapon (beam?  missile? gun?) to your defense (shield? anti-missile? armor?), and yours to that of the enemy.

In general, it is best to have your weapon not match the enemy's defense, while it is a good thing to have your defense match the weapons of the enemy.  That is, you will be at a disadvantage if you put guns on your ships when the enemy uses armor as defense, especially the enemy uses, say, beam weapons and you use anything other than shields.

Also, you must have enough attack factor to be able to get past an enemy's ship defense and score at least some hitpoints per combat round in battle.  That is, if you put just one or two fairly low value weapons on a ship and the enemy has some defense, you might never get through the defense in any combat round in battle.

Oh, and always take "luck" as a racial trait.  Look that up for the explanation.

Ok, i might not have actually read everything, but i've read a lot. I just didn't recognise DL, DA and TA because i have the ultimate edition...

And by the way, i've just completed my first mission in the campaign

I think your tactic is the only way to go against the DL. In the first map of the campaign i start against bot the DL and the Korath. What i did was simply colonize all the available planets by buying colony ships. Then i researched medium hulls and gave the Korath hell by stationing a fleet of War Axes at their homeworld and destroing everything they had. The DL even got the chance to invade one of my homeworlds, but they failed, and then i quicly deplyoed 3 fleets, intercepting their transports, and started to build up my forces, and doing heavy research. When i was ready, i started making transports and invaded the Korath. After that it was harder than i thought as the DL had only a class 2 planet, even so they managed to wipe out most of my attacking fleet, but were crushed beneath the sheer number of my ships, and i managed to invade their single planet and win the game.

But i will remember to attack quick when thei have better planets

My ships have pretty low attack, and theirs have higher attack. Mine have no defense whatsoever, and theirs have a value of two for the 3 types. Also, they produce much faster than me... This game is hard.

Lol, if you are going to be up against the dread lords, it is going to be hard

Otherwise, it is okay - neither too hard nor too easy, IMO

The above shows why you lost the battles.  Every hit on your ship went against its hull (hitpoints), while most or maybe even all of the hits you scored bounced off their defenses. 

The mechanics of battles favors defenses early in the game.  Your ship must score hits greater than the defense value for the remainder to go against the hull (hitpoints).  If you're shooting with an attack of, say, 6 and their defenses are 2 of the matching defense and 2 of the both others, your best result may be 1 hitpoint and (more likely) you will get all 0s, unless you chose luck as a trait and are also Universalist Party, and/or unless you chose a very high attack trait or have seriously upgraded Red bases.

The suggestion I and others have made is not to start with the campaign, but to play a few non-campaign games first.  There are clear patterns to research and expansion, and how to balance costs and building stuff.  In some campaign scenarios, to the best of my knowledge, expanding too quickly simply enlarges the bullseye on your empire for others.

Oh, and if the DreadLords are ever on your map, they are the key enemy, best I can tell.  Take them out first, even expansion is not as important.  You must get Invasion and snuff them early.

Well, I´m assuming you play the TA campaigns, as in DL there are no Korath. Actually in these campaigns the DL are way easier in the beginning than in DL, and there appear also a lot of 1ATT tiny Dread Lord fighters, which you can easily shoot down.

Later in the campaigns they´ll built *much* stronger ships - but you´ll get some special Arnorian Battle Ships that are all your bread'n'butter in these missions. Don´t lose them.

Have fun.