Wow thanks for the awesome replies, guys!
I read somewhere that psy usually has no melodies, but trippy sounds and like, 1 measure melody rotations. But it is up to the artist what to do...
I partly agree that fullon is pretty easy to bust out a song. All you need is 4x4 beat with 0111 or 0011 bassline, quick breaks at the end of a bar, and some fancy FX here and there haha. But to make it unique, I believe you need to sample or use interesting synthesis for your FX and just overall, make it unexpected. (But even expected sounds can build hype!) I like the "emptiness" of fullon, but it needs to be used in moderation to create energy in the audience.
...Why don't we learn from goa if it's so intricate, and add those elements to fullon? The kick and bassline is really all you need to make it dance/trance. I don't know.