Someone can correct me if I'm wrong but I think key changes are fairly rare in electronic music. Honestly, I can't speak for someone who knows theory, but as someone who doesn't know theory I don't think that not knowing theory is a problem when it comes to stuff like this, if you're wondering.
If you want to be lazy, like me, you should learn what different scales sort of sound like, then when you need to, just google what notes are in the scale of a certain key. Once you have that, play around with it. Before long it shouldn't take you long to come up with something you like.
As a starting point, if we're talking dark, evil sounding trap, you should check out the harmonic minor scale. As far as I know, it's sort of the standard for trap.
Also, individual notes on their own mean nothing. Individual notes aren't music, it's an interval between two notes or a series of intervals that gives music it's character (an interval is the distance between one note and another, and when I say distance I don't mean over time, I mean in terms of pitch).
I'm sorry if this information is relevant to what you're asking, your question is very vague and I can try to help you more if you elaborate.