I'm new and dying know which one I want to get just want to note my mate mains phoenix and I normally try support or defence but if I want I just go for offence

I was solo qing today and I got into a game with a reyna that was not doing too good after the first half. (pretty sure he was like 3x negative or something) The score after the first half was 6-6. Not too shabby. But then a dude on my team...