Definetely recommend Makkro’s Ornn guides. However you are level 14, it can be overwhelming at the start. I suggest looking up to combo guides and learning first few ones that are simple and will be used in lane a lot more. Generally Ornn’s gameplan is farming for levels so he can start upgrading items after level 13 and he can survive bad lanes by himself.

For now a simple and decent build would be Sunfire Aegis and boots into either Jak’Sho (more tankiness) or Radiant Virtue (team buffs) and then building situationally.

Abyssal Mask (cheap and team buff) and Force of Nature (more tankiness vs mages) are good magic resistance items.

Frozen Heart (reduces enemy attack speed) and Thornmail (reduces enemy healing) are good for armor.

Then you can finish the build with Gargoyle’s Stoneplate as it gives great resistances and a huge shield spell.

For the first few levels you should try to farm with Q spell and you should really get used to using your main rune Grasp of the Undying. Grasp starts activating after a few seconds you are in combat, hitting minions or enemies and taking damage counts as combat. You can see its icon above your spells. Once it is ready your next basic attack deals extra damage, heals you and grants extra hp.

Generally you poke them with Q and do a basic attack to use your Grasp attack. When you get your W spell, you add in to that combo. Slow with Q, use W and proc Grasp. This short trade combo is very effective and doing it a few times will do good damage to your enemy but don’t do long trades when you don’t have your spells.

Level 3 you get E, you can add it to the combo as well. Your Q creates a pillar and charging into it knocks up the enemy. Generally you do Q slow, W and E to pillar and they will be knocked up, you can use grasp attack and back off before they attack you back.

These are the basic combos, try to use these in early levels. His ultimate is a bit tricky though, you will get used to it as you practice.

As I said you should mostly focus on getting gold and leveling up in first 14 minutes and then you start to play for your team, Ornn’s specialty is his team fighting and he gets stronger as the game goes on.