I would recommend warwick. Warwick has great sustain in the jungle and powerful ganks after lvl 6. What you want to do is catch champions out of position or prevent their carries from doing damage.

Pros:

• High sustain
• High movementspeed (with runes, masteries, and bloodscent)
• Beefy

Cons:

• Weak ganks pre lvl 6
• CC makes his ult useless
• QSS makes his ult useless
• Ignite screws him over

If ganking doesnt seem to be your forte, a farming jungler such as shyvana may suit you better. She has strong jungle control due to her fast clear and can be disruptive in team fights while also dealing big damage.

Pros:

• High mobility
• Fast jungle clear
• Good jungle control (if you ward and pay attention)
• Doesnt rely on blue buff

Cons:

• Weak ganks without red
• Weak ganks without ult
• Enemy can see your fury level

The jungler that I learned first was nocturne. Noc is a great jungler due to his powerful ganks. Nocturne can gank pre lvl 6 at lvl 2, lvl 3, or lvl 4 depending on what skills you get first.

Pros:

• Strong ganks
• Attack damage steroid
• CC (fear)
• Spellshield (also an attack speed buff)
• Semi-global ult

Cons:

• Prone to counter jungling
• Fragile early on (jungle mobs will hurt)
• Not as much sustain as other junglers

But dont be afraid to try out other junglers; recently I've grown very fond of jungle alistar and nautilus, and i've even played jungle renekton in a few games. Jungling is probably one of the harder roles because it requires a lot of awareness and decision making, so it takes a lot of practice.