Dragunity Knight - Gae Dearg

1 Dragon-Type Tuner + 1 or more non-Tuner Winged Beast-Type monsters
Once per turn, during your Main Phase, you can add 1 Level 4 or lower Dragon-Type or Winged Beast-Type monster from your Deck to your hand. Then discard 1 Dragon-Type or Winged Beast-Type monster.

Can I get a winged beast and discard a dragon, or vice versa, or do I have to discard the type of monster I get?

You can add a Winged-Beast and then discard a Dragon and vice versa. There's nothing in the effect that force you to discard the type you add.

thanks