what are you spending your seals of conflict on?

So, I want to know what's the best way to spend them. I already have 4 of each exclusive artifacts (4 cap artis / 4 im artis) and I don't think I'll be needing more since they not BiS for anyone.
Now... I won't buy the blue box (uniques) cause I don't need any.
Same thing kinda happens with the red box. It doesn't bring the only artis I'm interested in (ILAS and UEB) so it's kinda pointless for me to buy them. (though they make more sense than blue boxes cause artis are tradeable).
Should I spend everything on cores, hoping to get an armored trifecta? Or just play "safe" and buy red mystery boxes?
If you're a veteran player with tons of artifacts (except ultron ones cause I don't farm it) what would you spend your seals on?
It would make much more sense if red mystery box contained ultron artifacts.