need build/equip advice

I know there's threads but I've looked through a few and it didn't help much. I want to make a backstab assassin.

my ideas on a build so far is-

200dex

100-120agi

100-150crit

and then rest for int

the equip I thought I should use is-

fuma s upgr

shushiwa s upgr

wind key up s

ghost candle

so far I only have the wind key.

im not sure what xtals but I thought colon tree myt help with skill delay. any xals to increase the power of backstab I should use?

im not planning on starting mq until lvl 100-120 so ill have plenty of points to distribute.

any ideas on a better build or other equips I should use?

and thanks in advance for any advice u can give.