Khazix isn't awful and you can potentially do well with him, but right now a tank jungler will have much more of an impact in the game, and you will never beat them 1 on 1. He needs buffs; if the other team takes Volibear or Sejuani against you will will have next to no game presence
If you want to try him out, go for it; he does take some practice to get used to, and by the time you have that practice he'll probably be buffed up some.
For tips, remember to always evolve Q or E first and second (in some order). Don't be the teamfight initiator; you're an assassin, so wait until a priority target is isolated then go in on them. You will need to build at least one tank item to survive late game (Randuins or Frozen Heart work nicely), and armor pen is really good on him (Last whisper is good, Black Cleaver is expensive but great on him).
Extra Tip: you can Q an enemy during your leap (E) if you're in range to do it.