Alright here is my help, but as most pros will always say, experience is still the best teacher, try other builds, test them on pvp(or lhz_dun03 if you aren't sure of yourself) then reset.
str- 230-280 at most, having 300 str makes you vulnerable since it would lower other stats
agi- add this after dex, put enough until 195 aspd(if you aren't elite yet, I suggest using awakenings and such so you don't waste stat points)
vit- at least a total of 100 to protect you from certain status effects, but if you need more then do so
dex- a total of 150 never more than
int-1 or depends on your preference
luk- 1 or depends on your preference
for cards needed, of course Incantation samurai, tgs, skeleton workers, phreeoni, valkyrie randgris, ws if you want, FBH on shoes, Gemini on headgear, maya purple. Experiment on certain card combos and you will find the thing that works for you. Kiel isn't much needed in double daggers since you won't be spamming skills. A forsaken soldier card is good so you won't waste two slots on Gemini(A lot of people use stone nowadays). having different armors for different enemies is also good.
That is all the help I can give for now, as I said, Experience would make you better and help you find which is best. Took me a long time to settle on a build, only to change it when I came back two months ago. Adapt to the environment, and don't stick to one build. There is no "cookie-cutter" build, everyone will have an advantage at something. Also when making a build, do not focus on the goal to kill any class. It won't work, there is always someone or something that would kill you there.