New to trading, what are the high value pokemon to keep as currency?

Hey guys,

I dont have any of the mainline games. I am playing pokemon champions, I managed to have a "decent" collection of pokemon through GTS trading of anything I caught in PoGo. It took alot of effort and time.

Apart from floette which seems impossible to get. What are some pokemons I can obtain and their value would not go down. So I wanted to have a target to keep trading up to get them.

I was thinking of Bloodmoon Ursa luna, Raging bot, Walking wake or Gouging fire. I was planning to have a few of these pokemon 3-4 saved up where when the regulation changes in pokemon champions, I am able to trade for the difficult to get pokemon,.

Can someone enlighten me?