how do i get to lilycove city and were are the elite four???

To get to Lilycove city, you must go east of Fortree City. There will be a long path of trainers and wild pokemon. If you keep on going in that pathway you will be in Lilycove city in no time. The Elite Four are east of Mossdeep City but you need all 8 badges to continue on. As you get all 8 badges go to Mossdeep City, head south then go east for a while, you will face alot of trainers and wild pokemon. You have finally reached to Ever Grande City! Now you must pass the Victory Road which will be difficult with all of those puzzles. Then you reached to the big building in Ever Grande City! Now go in and fight the Elite Four. They will be tough but you can do it!
Thank you for reading this answer.

Go east from Fortree City. It takes quite a while, as there as lots of trainers to battle and lots of grass to go through, but eventually you will get there. Basically, keep following the general trail - through all the long grass. As long as you keep going east you'll get there.