You can play Gothic 3 a lot of hours not thinking about fractions, allies etc. But sooner or later this time comes. There are three possible endings, one for each main fraction (the Rebels, the Orcs and the Hashishin). These are the tips showing the fastest way of finishing the game according to three paths.
You start in Ardea. After liberation the city do a quest for Gornn. It let's you to reach Reddock.
Your main task in Reddock is to earn the Rebels's and their leader Javier's trust. Do all quests increasing you reputation and then Javier tells you what to do next. You have to go to Cape Dun and find the rebel underground there.
In Cape Dun you have to start with earning reputation points for Orcs (even if you want start the rebellion). Do all quests increasing reputation until you are able to meet imprisoned paladin Wenzel. Talk to him and to the rebel underground Phil and prepare the rebellion. When you are ready start the fight.
You learn nothing important in Cape Dun so you have to go to Montera. Your first step in Montera is to work for the leader of the mercenaries (this way nobody is accusing you of cooperation with the rebels). Then try to contact with the rebel leaders camping around Montera and do quest for them. Work for the rebels until you get the name of their spy in Montera. The spy tells you to how to start e rebellion in Montera. To do that you have to earn high level of reputation in Montera. So you have to start working for the Orcs and mercenaries. When you are ready start the rebellion and help the rebels to banish the Orcs from the city.
After Montera liberation go to Gotha. Destroy the group of Orcs and head to the castle. But do not enter the castle yet - there is a powerful demon waiting for you. Just clear the area in front of the castle and enter the tunnels under Gotha. You can find there the teleporter rune to Vengard temple. Use it.
In Vengard you have to go through the entire city occupied by Orcs, until you reach king Rhobar. Talk to him and listen to his orders. Take another teleporter rune from Karrypto and go to Nordmar to find Xardas. Your first target is Faring.
You have to visit Faring because it's the easiest way to Nordmar. You have to earn a high level of reputation in Faring before you are allowed to enter the pass to Norma. Do some quests for the Rocs and mercenaries and when you're ready do to Nordmar.
You have to reach the Hammer Clan. They can't help you too much so you may head to the Wolf Clan. You may go there at once but it's a good idea to pare some time for the liberation of the great mine of the Hammer Clan. When you are ready go to the Wolf Clan.
You can meet here people knowing Xardas's hideout at last. They also can show you the way.
You found Xardas at last. Listen to his story. Then use the teleporter rune and go back to Rhobar to report. It's time to start a searching for Adanos artifacts. Geldern is you first target.
Orc shamans know something about the artifacts so you have to talk to their leader Grok. You need a high reputation to be allowed to meet Grok, so do quests increasing reputation in Geldern. Then talk to Grok, listen to his story and take his map. Now follow the places signed on the map. Start with Trelis.
Doing quests in Trelis you will know that Vak the leader of the town has the artifact. You may buy it from him, but there is another way: talk to the rebels in Nemora and start the liberation of the city. Kill Vak and take his artifact. Now you may go to Varant desert.
The second artifact is in the temple of Mora Sul. Talk to Kalesch the excavation supervisor and he tells you about the keys. Find the keys (you have to do a lot of quests in Mora Sul), open the temple and get the artifact. You may go to Al Shedim excavation now.
Find Saturas here. Once again you have to collect the keys to the temple (doing few quests). Open the temple and take the artifact. Now you may leave Varant - go to Gotha.
You already were here but now you may enter the castle. Go there, kill the demon and take the ring from its body - it's another artifact. It's for the last one artifact - go to Nordmar again and visit the Fire Clan.
Meet the leader of the clan ant take the quest connected with the power of the ancestors. In the tomb of Akasha you can find the last Adanos artifact. Now you have them all and it's time to use them. Go to the Monastery.
Find the Innos altar in the Monastery and prey - Innos talks to you giving you orders. You have to banish the Orcs from Myrtana and kill Zuben.
Go to Ishtar in Varant and kill Zuben. You need a high level of reputation if you want to enter this city so it means that you have to do a lot if quests for the Hashishin. The other way is to ally with the Nomads and help them to get rid the Hashishin out of the Varant. After killing Zuben finish the Orc job.
There are three invaded cities left: Geldern, Sildern and Faring. Banish the Orcs cooperating with the Rebels (where it's possible). When you finish your work go back to Innos and report.
This is the end of the rebel path.