Hello, I have just recently played according to your guide and I have to say: It is indeed a decent guide for Ornn in the Jungle. Only the Jungler Item seems to be not that useful for Ornn since only his Ult scales with AP and that even very low (20% doesn't let him reach a decent power at all). I would rather suggest to use the Cinderhulk Enchantment on the Jungler item as your primary choice since Ornn is more of a tank. But I still play with Runic Echoes Enchantment just for fun, tbh I don't know why, but it just seems fun and I am always looking for some extraordinary builds :D I only changed the secondary runes with Sorcery: Ultimate Hat and Transcendence and added a few more AP and tank items in my own item section for Ornn. Especially mentioning Liandry's Torment as a very good choice for extra AP, HP and a very good synergizing passive with Ornns great CC abilities (%-Damage is doubled against movement impaired champions!). I also considered adding Locket of the Iron Solari, Rabadon's Deathcap and Luden's Echo to the item section and I exchanged Sunfire Cape with Randuin's Omen as one of my primary armor items since I am don't really think that Sunfire Cape will be of great use for me. Just my opinion and thoughts on your guide.

Overall a good guide, I will stick around to your guide. I would only recommend to show a few Jungle paths/possibilities to start off and maybe really change the secondary runes from Domination to Sorcery. His Ult is a great engage tool, e.g. for Yasuo's Ult or a extended stun for Leona's Ult, and as far as I have noticed, Ornn's Ult CD will be under a minute with 40% CDR and the Ult reduction from Ultimate Hat. Also exceeding the CDR can be avoided by using Transcendence, which will give you a bit more AP.

Just tried this (using your items) and while there was a dlight increase in damage it did not seem worth it for the 30% health trade off that increases your bellow. if i am missing something pls correct me. this seems like an interesting idea.

Bellow's breath doesn't scale with ap, in fact the only thing that scales with ap in his kit is his ult with a 20% scaling on each hit. Don't build runic echoes.