Every ADC is viable in low ELO since player skill is the biggest determining factor, though champions dependent on their teams to peel properly will likely suffer.
could be a good choice since:
- He's quite bulky for a marksman
- He has innate armor reduction
- His passive reduces the damage he takes
- He slows anyone his by his AA or Q while W is active, allowing you to kite immobile champions like the Juggernauts
It can make it difficult for enemies to burst him down (especially without armor penetration) after he gets a few items and he still deals good consistent damage. He can also bully many ADCs after he has Manamune (or at least Tear of the Goddess) and multiple ranks in Q.
is also a good option if you can make it through laning phase (his laning phase is weak, but enemies at low ELO shouldn't be competent enough to appropriately punish you for it). Teams in low ELO are typically pretty bad at warding and coordinating, so Twitch can assassinate enemies allowing you to take objectives while you have 5 people to their 4. In addition, he's a monster in mid- to late- game teamfights since he can hit multiple enemies due to his ultimate. Even during laning phase, it isn't too hard to roam mid (after basing or pushing the wave to tower) to kill the enemy mid-laner to help snowball your ally.