Good Champions? (Builds too please)

Hi! This is a question post that I have. I am a current Lux level 7 with a MF level 7. However, I watched this really funny LoL parody, but what the Jinx said made go, "ah, I should do that." She said something about "honing skills in more than one champion." So, I want to expand my LoL champion pool.

Currently, I only play (in the lanes) these champions:

Top:

JG:

MID: or

ADC:

Support:

Who should I add in these lanes to become more of a well-rounded player?

Also, Diana mains or good Dianas, I am thinking of getting her soon because I got a free skin from hextech crafting. How should I level / build her? Thanks!