Legal to gift a a deluxe edition spare?

Given away as in using Steamgift's function? Or given away as a normal gift? The latter should be no problem.

Given away using Steamgift's function of course. I would like to start giving back to the community after I have won a few games. Wasn't sure if only keys were allowed or items that were purchased directly if that makes sense.

Are these types of gifts allowed to be given away or not?

Yes. :)

You're always allowed to give away something you obtained through purchase, unless it has been given away free in large quantity (and without requirement of purchase or significant effort) elsewhere. The fact that you essentially purchased a multi-pack instead of a single-pack is just the same concept as purchasing a bundle and giving away spare keys.