Depends on which positions you enjoy playing. Rengo can be played Top/Jungle, while Lucian is an ADC. Both are fun.
If you like deleting people, Rengar.
If you like dueling as an ADC and fun teamfights, Lucian. You can also play him as an AP/AD mid to a lesser extent, but ive never tried it.
I laugh at people who solo/duoq normals hahahahahahaha
Play ranked friend.
Only if 2 or more friends are on
Heh, i'm not a masochist, idk about you though. Not gonna bother complaining about the vermin there. Not touching it again until I can hard carry a team and get close to the ideal amount of cs per minute.