Like I said before, if you still can't decide what build you want to make for your gambler, just learn the SAME skills before MT (I mean in level, if before level 10, then just take lvl 10 for now, no need to max it)
same with gambler, you can still learn all your skills like the SAME before the upgrade, you still get bonus 30 EP to max 1 skills you want to max
the problem arise from the update is "wanting too many debuff" that's why the solution is just choose what kind of debuff do you want
and if you can't decide yet, just learn the skills the same way as before the MT
that's my only suggestion for current situation