Togami's GTS Advice

If you want a better trading experience out of the GTS, then follow these two tips:

A. Get a Lileep. Why Lileep? Because most people pick Anorith in ORAS, and because Lileep is exclusive to X. You get trades from players who have Y/OR/AS.
B. If you want legendaries, Lileep won't always cut it. Grab the foreign Pickup Zigzagoons you get from WT and level grind them to 100. Offer those for whatever else you want.

Moral of the story: Always deposit, don't seek. Good trades go quickly.

In case you don't know this yet: To seek a pokemon not in your dex, go all the way to the bottom of the selection "A B C... X Y Z" and there is an option called "What pokemon?" pick that end enter what you're after manually. For example Unown, or Anorith