Destroyer Rush is only to get gold.....
First you build a Destroyer directly at your opponents tower (Under the least possible threat)
Next let it kill whatever tower it can, meanwhile, start on a burrow near it.
Following that, sell the Destroyer (If it can't hit anything).
Repeat.
Once you get enough gold, just go to a corner and tech.
Great way to attack early game and hold positions. Burrow for control, Destroyer to attack.