do you mean weapon/eidolon from shop? where you trade with items? if yes...
IMO if the sr weapon isnt assault = not worth (also the weapon is not kh weap), also i would rather search sr weapon from disaster..
eidolon also not worth because ull get SSR later anyway from events.

the only thing i would trade from the shop would be half elixir until it reach certain points where it become expensive and not worth the effort.