Slark is fragil in early game , bide your time til you are lvl 6 but dont be afraid to pounce if you have back up. sell the ring if you need the space , its mainly for mana regain and that little bit more damage.
You want to get your eye of sadi if they have fast heros and REMEMBER YOU HAVE REDICULOUS HEALTH REGAN SO USE IT (lvl 6 and above) and side note go to the lane with the side shop and buy the 2 tangos and ring at start then the orb of vemon about 10 seconds into the game at the sideshop ASAP!