Full set is pretty good, with a 35 spirit monarch and magefist you will hit 105 fcr which means rings and boots slots are free for whatever you prefer. Also full set gives lots of res so you would just need a few charms to max resists.
Don't know about "cheapest" option, I guess that would depend on what gear you have access to and where you intend to farm.
i was builkding now this:
shaco
tal amu
tal armor
tal belt
death phantom
soj
naguel
trang gloves
spirit M
do you think its good? would you change belt for arach and lose the 3 bonus of tal set? ocu instead of death phantom?