i suppose youre talking about skills that "drain crush gauge"? crush gauge is the white gauge under hp bar on enemies, the one that allows you to do executions no matter what hp left they got, so any skill that "drain crush gauge faster" will allow you to get enemies to that vulnerable state.

my recommendations for skill tree, regardless of what character:

i prefer to invest most points on the top half rather than the bottom one, since brain field and brain drive skills are on that bottom half (although maybe you havent gone so far to unlock brain drive and brain field). i basically do this bc these 2 skills are special and can only be active for some time, so any upgrade you get for them will be available only when theyre activated.

not saying to completely ignore them, for example you can get the 1st upgrade for each of them, which will be cheap and will allow you to use them more (brain field time extension and brain drive accumulation rate up)

on the other half, i recommend: try to work towards unlocking concurrent sas activation (they are place on the right side i think) that will allow you to activate more than 1 power at a time (one upgrade lets you activate 2, and 2 upgrades allows you to activate 4) so id try to get 1st upgrade by phase 3 or 4, and second by phase 8 or 9 more or less, since you'll have more powers at your disposal as story progresses.

if you like using psychokinesis attacks, go for the power gauge boost (again there are 2 upgrades with the same name, you can get 1 or 2 to get 75% or 100% of max power gauge unlocked). if you prefer regular attacks, go for the upgrades to unlock adittional combo attacks (your base combo is 3 attacks, it can go up to 4 for kasane or 5 for yuito). also charged attack is pretty good specially on yuito.

as a general thing: right side of the tree will give you utility, more exp, money, additional plug in slots, etc. the left part will give you stats boosts, more attack damage, more crush gauge damage, more psychokinesis damage/gauge, and skills on the top, between those mentioned, will give you additional moves, more combo attacks, double jump, mid air dodge, charged attack.

hope that helps!