Which champion should I purchase?
Just want to try someone new, I don't jungle.
Rengar Varus Swain Talon Volibear Gnar Velkoz Xerath
Just want to try someone new, I don't jungle.
Rengar Varus Swain Talon Volibear Gnar Velkoz Xerath
or 
Gnar if you like shapeshifters (Jayce, Nidalee) and/or resource management (Rumble, Shen), and being the cutest yordle ever (fk u teemo). Vel'Koz if you like geometry.
Volibear
Swain
Because he is one of the hardest champions to CS with and it's great to practice CSing with him.
Also he's very underrated.
I would pick Volibear out of that group, but you said you don't jungle.
If you want a pokey midlaner, Xerath is cool. His pokes can dominate a lane, and he has high mana efficiency thanks to his passive. Only downside is, Xerath's only defense against melee champs is his stun. He has no good mobility.
I really like gnar at the moment but velkoz and varus are good non-jungle choices that i find fun.
Vel'Koz is amazingly fun to play. There's nothing quite like unloading your entire combo with that giant laser for the kill.
I recommend Teemo. Because he's Teemo.
But on topic Talon is really fun to play.
Out of those options I'd say Vel'koz personally.
Which of the following appeals the most?
Rengar: KNIFECAT JUMPS FROM THE BUSH AND KEEEL YOU (in like 0.25 seconds) Varus: FANCYMAN POKES AND SNARES AND THEN KEEEELS YOU WHILE YOU RUN (with a well placed, long range Q) Swain: BIRDMAN FEASTS ON ENEMIES. SLOW, IMMOBILE, BUT HE KEEEELS YOU (over time with DoTs and ravens) Talon: BLADEMAN IS TWITCHY ASSASSIN WHO WILL ALL-IN YOU WHENEVER HIS ULT IS UP AND KEEEEL YOU (quickly, while you bleed) Volibear: BEARMAN - NO, JUST BEAR - CHASES YOU DOWN. EASILY KITED BUT IF HE REACHES YOU, (his team will) KEEEEEL YOU Gnar: little furry things becomes BIG FURY THING! AND BOTH CAN KEEEL YOU (if you can manage his transformation) Velkoz: EYEMAN MOVES LIKE A ONE-LEGGED ELEPHANT, BUT HE WILL KEEL YOU (WITH FREAKIN' LASERS) Xerath: RUNEMAN IS BASICALLY AN ARTILLERY CANNON AND WILL KEEEL YOU (If you can land that $#@(ing ultimate)