If you're thinking of getting into jungling, the first character you buy for the job is important. Who you pick determines a lot about how you go into the job, what types of skills you develop, and how you think about the entire jungle concept. If your first jungler is a speed-clearer like Shyvana or Master Yi, you're going to look at things differently than if you choose a powerful ganker like Nautilus.
Regardless of the character you select, the jungler is a playmaker. If he's not making plays that get his team ahead, he is going to hurt his team if the enemy jungler is.
The basic types of junglers
The first type of jungler is the powerful duelist ganker. These junglers excel at fighting, deal lots of damage, and are very effective when actively ganking. They have some kind of CC effect, though it may only be movement slows and not a hard stun or fear. They can also launch a gank attempt themselves without too much aid from a teammate. The duelists vary quite a bit in clear speed, and the slower yours is, the more you will need to rely on ganks to compensate. Olaf, Lee Sin, Udyr, and Jax are all good examples of strong duelists who can set up ganks.
The next type is the gank assist. This jungler is typically loaded to the gills with CC and can lock an enemy down for a long time. He generally doesn't do as much damage, though this varies. Rammus deals very little compared to Nautilus, but they both serve similar roles. Alistar also serves as a gank assist if he's chosen as jungler. This jungler usually clears slowly, but not always.
The third main type is the speed clearer. This jungler burns through jungle camps rapidly and often has movement steroids to travel between spawns faster. These junglers are not very good at ganking, but many are excellent duelists and can deflect ganks or assist struggling lanes. In terms of aggressive play, the speed clearers use counter-jungling to weaken the enemy jungler or steal buffs. Due to their faster clear times, they also tend to have more gold and can buy more wards. Shyvana is perhaps the perennial example of this type of jungler.
The final type is the true assassin. Although it's rare, some assassins clear the jungle quickly enough and/or have special mechanics that aid in bypassing wards (typically blinks or dashes that travel over walls). They are similar to the duelists but generally don't duel very well and rely on a combination of CC and insanely high damage. Few assassins are decent junglers, but I am a fan of jungle Evelynn, who has good clear speed, high DPS, and the ability to run past sight wards undetected while her stealth is active.
It seems odd to ask this before the end, but as a first-time jungler, you should probably be thinking about whom to buy before you ask exactly how every jungler in the game works.
For a long time, my only jungler was Alistar (whom I got for free for subscribing to Riot's Youtube channel), and I didn't really like him. If you are just starting out, you can try jungling with him in bot matches to see how it plays out. He's pretty reliant on scoring ganks for his team and can do so as early as level 2. He's sort of an expert-level character, though, and relies on a somewhat glitchy interaction between his W headbutt dash and his Q groundslam. I'm pretty sure it's a bug (not part of his initial design), but I know that Riot knows about it and accepts it as part of Alistar's gameplay.
My first real jungler was Udyr, however, and I absolutely recommend him for anyone wanting a good, versatile starting jungler. He's a bit unusual to play (R at level 1, can't level all of his skills, stance mechanics), but he's not really that hard once you get used to it. His R helps him clear fast, his W makes him very sustainable, and his E makes his ganks hard to escape. His Q also gives him quite a bit of up-front melee damage. He has quite a large number of builds, both in items (tank or bruiser) and skills (max R, max Q, 5/5/4/4 versus 5/5/5/3, etc.), so he has a lot of ways to experiment. He is also a good solo top if you want to take him there. I stand by Udyr 100% as one of the best first jungler picks. He's been very good to me and he is still my go-to jungler even though my jungling stable is much larger now. He's also only 1350 IP, so he won't take much time to unlock. Udyr does pretty much everything you want in the jungler. If you want him to clear fast, he can do that. If you want him to gank, duel, assist lanes, or whatever, Udyr can do it if you build him for it.
If you want a really good tank/gank jungler, I recommend Amumu. His ganks are immensely powerful and hard to escape, and his damage isn't awful, though it is on the low side. He's easier to play at lower levels when players don't ward, but his presence in the game keeps people honest even at higher levels. He's cheaper than a similar ganker like Nautilus, too. I do prefer Nautilus in this role, but Amumu has a much lower bar of entry at 1350 IP. If you get Alistar for free, his bar is lower, but if you want to tank but don't like the cow, try Amumu.
If you want a more clear-focused jungler, I actually also recommend Udyr and leveling his phoenix stance. I am of the opinion that Shyvana is the only really good speed clearer, and she is very expensive to unlock. If you are really into dragon girls and have a lot of time or some real money, Shyvana is a good choice, but I would not invest into her until you have a good idea of how she differs from other junglers.
If you have a lot of IP or some real money, Lee Sin is incredibly good. He doesn't rely on mana like Udyr and also does everything well. He's even a bit better at ganks, since he doesn't have to rely on running out of bushes and praying. Lee is very, very strong. If you want to focus on jungling, I definitely advise getting him at some point.
I somewhat regret not talking about sustainability in the last jungle article. If you're jungling, you need to know how many health potions you need at different times in your route. Some junglers are constantly at full health after their first run. Some are even at high health on their first run. Others ride the potion train for quite a while until they can fit in health sustain items and are frequently at low health during their route. Olaf is a good example of a jungler who clears faster at low HP and has minimal sustain, and that makes him vulnerable to invasions. Keep this in mind!
To some extent, you can predict how a jungler will clear. However, in practice, you simply never know until you do it. For instance, you can probably predict that squishy Evelynn has low HP during her route since she has no health sustain. You'd be right. However, Shyvana tends to have higher HP during her route, since health sustain items are early in her build and she is inherently much tankier even though she also has no natural health sustain. I'm often surprised how durable characters with minimal sustain can be, and I'm even more surprised to find out that characters with self-heals frequently can't keep their life up. A lot of the time, this is due to poor damage. If you clear camps slowly, those camps do more damage.
This is another reason I recommend Udyr, since his Turtle Stance shield blocks a lot of damage and Turtle Stance also heals him with every punch. For the beginning jungler, he is pretty safe.
For your first jungler, pick a generalist. Udyr is really the best choice; he's affordable and does everything well. Jax is also decent if you're into him.
I don't really recommend picking a specialized jungler like Fiddlesticks or Shyvana early on. If you really like their aesthetic, you're going to do it anyway, but I would practice jungling with someone more well-rounded. If you don't like to gank as much, you can still play Lee Sin or Udyr and focus on clearing and counter-jungling. However, if the enemy is pushing you can jump on that and feast on some $300 dinners. Having the options is important to learn all the facets of jungling. You don't want to just roam around and kill jungle mobs. That's really not your job.
We understand what it's like to climb the skill ladder in League of Legends. The Summoner's Guidebook teaches you the tools you need to get a competitive edge. Whether you're climbing the ranked ladder, playing Draft Dominion, or getting crushed by intermediate bots, every enemy has a weakness. And every Thursday, Patrick Mackey shows how you can improve improve on yours.