Music theory isn't a necessity, and I didn't using anything but samples for the first 5 years or so. But, I'd recommend people learning it as soon as possible. Even just picking out the root, third, fifth, and seventh of a key. Then, making random melodies / sequences until something sounds cool.

LPT: If someone is new, and looking to make house, techno, etc. I'd recommend sticking to minor keys when exploring music theory.