can you elaborate your strategy on Emperor level ? for example, what's the best technology line?...
I always build 'The Stone of Prophecy' first (even on Deity). I will regenerate the map if I don't have a production boosting resource in the BFC of my capitol city. First techs I get - Mysticism, Mining, Desert Survival, Water Conservation, Exploration, Defense Tactics, Spice Extraction, Water Transportation, Stillsuits, Arrakis Habitation, and then Education. Usually this allows me to build 'Filmbook Archives' (2nd GP normally will be a Great Scientist which I then use to get Social Mobility for free). Other key techs - Offworld Trade, Academies, Culture of Dune, and Vendettas. However, by this time the AIs have caught up and have other key techs I don't have. I trade techs with the AIs fairly aggressively.
Key goals - espionage superiority (absolutely critical - it will help you choose research priorities e.g. why let the AIs get Solaris Economy when you can beat them to it), strong defense first, air superiority and then finally an overwhelming combined arms offensive force (built using Kanly civic). Declare war, take a few cities from the target civ (based on game conditions) and let them capitulate. Choose the next victim and repeat process (with your vassal(s) joining in on the fun

) until victory (three vassals usually does it). There's a bit more to it of course, but this is generally what I do.
One last point, in game conditions greatly affect the order I get tech. If House Atriedes has Hawk thopters, I don't wait to get rocket troopers - part of the 'strong defense first' philosophy.