I'm using my Arbok with Relax Nature.
It has a lot of defense, but lacks speed.
Everything else is above average which is a plus.
My current moveset is..
-ACID(Insane Damage +STAB)
-EARTHQUAKE(Strong against Poison, and others)
-REST(Taken out PKMN +10 levels thanks to this)
-GLARE(Always optional, useful, flexible to change)
I might switch GLARE out for something else, but
paralyzing your foe is very important in case of
my Arbok battling a Kadara who can one hit KO.
ACID is obtained after the 5th gym, but I am not
sure what other strong Poison moves ARBOK
learns automatically or by TM, I am going to
breed my Arbok after I beat the elite four to
teach it Poison Fang.
EARTHQUAKE is always useful when fighting
another poison type, the other trainer wont
expect it. Plus it can squash that Arcanine
or Ninetales you see every now and then hehehe.
With REST my Arbok usually wakes up right
after the first turn, allowing to continually beat
down the opponent. I have had encounters with
numerous trainers who quit because they cannot
beat my Arbok which is sweet.
(P.S.)
Make sure if you go this way that your Arbok
has the ability SHED SKIN so right after you use
REST it awakens with a 33% chance. The ability
INTIMIDATE is nearly useless to me haha :P