Ok, I'm not a great league of legends player, but I do know a little about numbers. So let me ask you this. Does Janna go full AP? No. She builds utility. Why am I asking you this? Because their kits are very similar. Some CC, spells with utility but low AP scaling, of which include a shield which scales in two different ways.

Ivern's scaling average at best. There's no way to go about it. He doesn't have the nuking capability in his kit to function as an AP carry. At least, not to do it reliably. I mean, not without dying in the process.

Basically, play like a very roam happy bard, with your bessie mates being champions like tryndamere or low range carries who need a little help to get their lane opponent in mulching range. Ult, Q, shield someone, and hope for the best. Yes there's more depth to Ivern like that (bushes that get you killed more often than not), but i don't feel qualified to give an in depth guide. This is just trying to get people to play him more like a roaming support than a trash tier AP jungler.