Of all the options, you can usually get the most value for your card as you are selling to an individual and a normal card price is to be expected
Blue gets you proliferate, but outside of Inexorable Tide, the mechanic is just plain better on the artifacts that have it namely Contagion Clasp, Contagion Engine, and Throne of Geth
Like Hearthstone, Legends also includes an in-game currency which can be used for multiple things
Start from the 100-card total, subtract your single commander, then fill the 99 using the ratio above: lands first (36-38), then the ramp, draw, and removal cores (roughly 10/9/9), then 7-10 win conditions, and the rest as synergy and flex slots
If anything, the worst youll get from them is warts (if you believe old superstition)
But it does capture the One Hit An' Yer Dead! spirit of the original