What champion should I choose?

Hello all! I've been playing League of Legends for a couple of months now, and I've been recently wondering what champion(s) to use my 7,000 IP for. Personally, I usually play as the AD carry and prefer long-ranged champions, but I honestly wouldn't mind trying something new. The champs that I enjoy playing are champs like Teemo, Ashe, Sivir, Ahri, Kat, Graves, Annie. But besides playing ADC, however, I also enjoy playing mid with Kat/Diana every once in a while. In general, I enjoy having most of the kills on my team (if I can, of course) and doing a lot of damage. Regarding this matter, I came here to ask you guys what champion do you think I should buy. Here are the ones I'm considering, but of course, feel free to suggest any others:

Ezreal Syndra Ekko Akali Caitlyn Evelynn

I know those are many good champions to choose from, but I'll appreciate your advice on which to buy first & why! Thanks a lot :)