Could you include your rank in your guide? More info about you helps.

Then wolves, save the smite, which will be off CD now. Instead, give the big one a smack, devour it, and keep it in your belly while you focus on the little ones for about 4 hits. It's usually best in early game with the little camps to keep the large monster in your belly while you take out the smaller ones, to save you taking extra damage. Take an E after this one.

Only ever use your E if you are very low on health, or you see an ult incoming that would kill you (like Garen's ult. Your E shield counts as health, so his ult will do very little damage).

If you get invaded, assuming you're not low, always engage them. Don't use your devour! What you need to do is start hitting them with basic attacks, as soon as you build enough passive, q them for a stun. Then, if they still have over half hp, instead of using devour, keep hitting them until you get to use Q again. Of course, if you have a teammate on the way, or you yourself are low, then devour can be very useful for holding an enemy down.

Finally, how to use your ult. It's main power comes from it's passive, but I mainly use to jump around the jungle and farm quicker. It's other use is to come to an ally's aid and hopefully get there in time to eat them and save them, or to teleport ahead of a fleeing enemy. But my favourite use of ult, is to teleport the adc with me next to an unguarded inhibitor or nexus. That's fun.