Being a cheap-arse and IP-in everything, I've spent most of this morning reading Ryze and Ashe guides.
Thing is, and it's always been the case with me, I don't really want to play this PvP, I prefer to co-op.
Why? Well with most FPS PvPs, the playing field is fairly level the whole way through. With this sort of game though, a poor performing teammate can leave you behind the curve and getting roflstomped. I don't want to be that poor teammate, and also don't want to have to suffer from one if I'm not. Too much pressure and I stop enjoying a game, I'm such a wuss, haha.
playing support is probably the closest you will get to 'pve' type playstyle, although there will always be pressure no matter what you play