The first 2 should go into imp. sinister strike in the combat tree. For me - thats it for combat. My talent tree will eventually look like this:
2 ss
5 mod
5 malice
3 evis
Then finish assassination up to cold blood, getting leathality to 5 then ruthlessness and relentless strike, then imp instant poison 3, then cold blood.
After that, dump the rest of the points into the sub. tree, to get preperation ASAP.
You can go for another poison if you want, I recommend Crippling poison if you plan on high level PvE and instance raids.