I can't decide which champion to use! help!

Hello, I have just come to write on the forums after playing three LOL matches. I have used Dr.Mundo,Tryndamere and Jax. I can't decide who I like most. I love to play AD champs that are excellent at hunting down lone targets,and also being able to juke very well.I'm having trouble in deciding who I should get better at. I like Mundo's massive power and regen,but I also like tryndamere's ability of passively acquiring crit chances and his ult allows me to chase people past turrets. Jax is also favorable as he is an amazing 1v1 fighter and I love his E + W + Q combo. Can you please help me decide? I'm also considering buying Rengar with my 1000 RP card. So HELP! My average match goes like this: I farm until i get at least 2 to 3 points in to most of my abilities,which i manage at around 16:58 of the game. I then turn in to a Ganker+Jungler and pick of people from lanes. So help please.

So is it

Jax

Mundo

Tryndamere

Rengar

Thx

I'm also open for friend requests1 :P

peace.