So, as I'm level 22 I need to start learning a role well for ranked. Every game I play usually lacks a jungler, so I'm thinking of trying it. But, would it be more efficient to use Udyr, Nocturne, or Shyvana? Please state reasons why also.

I'd go with Nocturne. He's just extremely easy to learn and has incredibly strong ganks post level 6. His passive also grants limited AoE damage and life steal and his W allows you to block incoming spells. You wouldn't believe how many times I've hit W just in time to avoid a Karthus ult or to absorb Caitlyn's ult for an ally without taking damage.

Neither Udyr or Shyvana offer overly strong ganks and I personally feel that Shyvana's very held back by her lack of damage abilities. Her E does practically no damage and her W is more for mobility and wave clearing than anything else.

If you're new to the Jungle, learn Nocturne. He's a great champ.

I totally agree with TKiWhiskie

Nocturne for sure. Shyvana and Udyr are great junglers but offer nothing in terms of ganking potential compared to Nocturne.

While it is great you want to start jungling, I'd try to remember that Riot has plans to change the jungle for season 3, so some junglers that are viable now may not be able to do so later on when the changes come in.

I'd go for udyr, kinda easy for learning jungle and cheaper than the other 2. But then once I got 6300 ip I would go for nocturne next, he ganks better in my opinion and is waaay more fun to play!