I guess somone missed Ulver.For ambient:
Ulver
Biosphere
Deaf Center
Helios
Future Sound of London
IDM:
Gridlock
Orbital
Autechre
Psychedelic:
Shpongle
Astral Projection
Nystagmus
Yahel
At the very least try the three highlights. I would call those three groups likely the best electronica out there. Amon Tobin and Brian Eno are good too, but everyone recommends them so I tried to give you stuff that isn't as well known. I would highly recommend against Chemical Brothers and Aphex Twin, mainly because those are acts for people who have not experienced much in the way of electronica. Chemical Brothers are alright, but not if you actually want to LIKE electronica. You can't appreciate them without having listened to many other acts. Aphex Twin is garbage, but it is readily accessible for the main stream, so most people have heard him and like to claim they like him so they look like they are WELL VERSED IN MANY TYPES OF MUSIC. I could recommend you some other more accessible electronica like Tiesto, but trance is kind of like the pop of electronica and, again, you can't really appreciate what is good and bad in trance without having listened to lots of electronica. Otherwise you will either think it is AMAZING STUFF when it really isn't or REPETITIVE BULLCRAP when it isn't. I always recommend exploring genres from the bottom up rather than from the top down; that way you get an appreciation for the whole genre rather than just what you can buy at your local music store.