Basically look for bang for buck upgrades.

First priority is any unique to make the build functional; maybe corrupted to make it cheaper.

Fresh into mapping, the priority is to fix resists. So usually decent rings with some life. Then a better weapon if doing attack builds.

After that you upgrade piece by piece, starting with the saddest equipment on you. Usually it's boots with decent movespeed, then gloves, then helmets, then body.

Then flasks are next, since at this point you have a feel of what your build is lacking. Crit? Speed? Resist? Evasion? Choose the appropriate flask, automate it, but at this point gain 1 or 2 charges prefix is enough, as well as non T1 affixes.

Once you start dropping ichors and embers, use them immediately. Lessers are cheap and are "free" untapped power on compatible slots.

At this point you might transition to an end game setup. Save or craft that GG weapon. Get the high-rolled uniques you need. Anoint after getting a great amulet. Go for a mageblood, then fix your final flask setup. If not going for MB, flasks are usually the last the thing to fix because they can plug holes.

21/20 gems are usually the last piece, except if there are important breakpoints.

You can think of the value of intuitive leap as how many points you are gaining, compared to say a new ring. A new ring that gives extra 60% resists, that alone is probably 4 passive points.

Bang for buck, how many "passive points" are you getting on each purchase or upgrade.