Assassin/Ninja Element And Gear Build For Assassin?

I'd like to know what would a good build for assassin be, preferably something high damage and high crit rate while mana cost is reduced

EDIT: Also I prefer not to have to worry about hive/mythic items yet

 

https://wynndata.tk/s/dYUGoT
I think this should be a pretty good build!
Both dexterity and intel are high, hopefully meeting your expectations. It also is somewhat of a melee-spell hybrid. The spells do lots of damage, and melee attacks are decent. Even though mana regen is 1/4, you can get mana back extremely quickly with a max possible steal at 9/4.
The problems with the build is the low earth defense and the need to complete Fallen Factory many times. Earth defense can be fixed with powders, otherwise I suggest putting water powder on the armor to use concentration and take advantage of your low spell cost. While there isn't much of a way around FF, it's a good dungeon, and you can get yourself xp while doing it!

 

https://forums.wynncraft.com/threads/orange-wybel-weapon-builds.208232/
swap out boreal aegis with something like stillwater blue or Ornamental plate