Go on reading Assassin Information In Last Chaos:

Skills/Passives
The attack skills of the beginning can be maxed, you will forget those skills(Last Chaos Gold) in a few levels. Later, they become quite useless. It's important to max all your passives skills.

Before lvl 31, it will take you 4,063 SP to max everything. The total amount to have a maxed Assassin is 28,986SP and is that you want all the production skills too, it's 32,787 SP.

Attack skills Advice!
Confusion and Dire Strike can be maxed too, but it's not all the rogues who use these. It's useful in party with other rogues, you can attack together and make great damages, but you won't use it a lot in solo. And since the mana cost is higher, you could keep your mana for better skills.

Double strike and Hyde Step are main attack skills. Hyde Step is more PvP based, because you need to be invisible to do it. Later, at lvl 102(Last Chaos powerleveling), you can get Fatal Blow, and it's quite deadly. 

Poison in PvE kills the hp regeneration of the mob. Your snare is more effective then the knight stun, but it seems to miss less then. You are trying to get a longer poison or snare lvl 6, like the others class, let's get across your fingers!

How to use your skills!
The big difference you have with ranger is a skills that everybody would love to have. Death Motion!

Death motion is your life saver with the lvl 70 skill. Death Motion aka DM is a lvl 38 skills. Congratz, you can now solo what you want. Always put it on your hotbar. 400 Hp left? While you look at the beautiful sky, you can heal back, use minerals, all you want. Someone is calling you! Go answer to the phone. And remove your pet, or you'll come back with a dead pet to renew! You can stay in Dm for more than 1 hour of real time. Thanks for reading and have a good time.