Hi there, I am a Plat 3 (Season 4) player with good knowledge upon the lower elos.
The "Bronze 2 Plat" series I am creating, is a series dedicated to teaching players how to carry yourself from the depths of the ladder, to platinum.
Note: This is NOT a high elo guide - This guide is for carrying YOURSELF out of low elo. EVERYTHING in this guide can be done by anyone.

Udyr as a champion, is very versatile, he can choose which ability to level without having a downgrade, he has various viable builds and varius playstyles. Udyr is extremely easy to play due to the no skillshot design, he is alot harder to master however as being able to tell the difference between a good Udyr and a great Udyr is very easy.
Udyr can be played jungle or top, for this guide, he will be jungle.
TIP: Alot of players underestimate Udyr's passive: Monkey's Agility. You want to keep this up at all times as with this Mastery / Rune Page setup, you will have exactly 1.00 Attack Speed for your first clear if you keep Monkey's Agility up.

When you back and buy your jungle item, you want to buy Ranger's Trailblazer, rush Trinity Force, upgrade boots, then you want to swap your Trailblazer for Stalkers Blade.

You want to sit on your Trailblazer and rush Trinity Force and Mobility Boots. The reason you do this is because you want early damage, and Trinity is the best damage source for Udyr. Then once you've got your Trinity Force, you're squishy right? Nope, upgrade to Juggernaut for 500 Health and Tenacity.

With the new changes coming in with Season 5 as Udyr, you can start on either side, however i recommend starting at the bot side camp, just to get a better leash.
TIP: Level up Pheonix in base and when you attack a camp, use it straight after you attacked it to generate 2 procs of your active (Can be done with Tiger's DoT too)
Smite the Gromp Krug when it spawns level up turtle stance, activate Turtle and pop into Phoenix, start hitting the buff, keep an eye on your Monkey's Agility - when it's about to run out quickly pop it into the opposite stance, when you max out your passive, you will have 1.00 AS. After your buff you want to do a camp.
TIP: If you do Razorbeaks, make sure to focus the smaller birds before the big one as you will take less damage.
After your camp you can choose to recall and get your second buff or go straight to your second buff depending on your clear, if you choose to get your second buff, gank only ONCE before backing, as you want your Jungle item ASAP thanks to the changes.

Now this is extremely important to follow. As Udyr your ganking presence generates from movespeed, so ganking a Champion with gapclosers like Zed, Leblanc, Lucian is harder but possible. You want to wait in the brush and wait for the gapcloser to be used before you go in, or you will not be able to reach the Champion.
If I gank a lane and don't get a kill, i farm a camp or 2 to pay back for my wasted time.
If you see the enemy jungler gank but you can't countergank due to whatever reason, invade and do a camp.
I like to farm until an opportunity rises, for example if I want to gank top, I will go to Krugs and hope the enemy jungler will appear first so I can countergank, If not I gank as usual.
When farming, keep an eye on your mana, you never want it to drop below 40% if you are planning to gank, as earlygame your mana costs are high.
If your lanes are winning it is wise to just farm and secure Dragons, if your team is behind Do NOT farm, focus on ganking an Dragon Control.

This is a decision that will impact the game depending on the choice you make. If you gank and get a kill, push out the lane and do some damage to the tower. This generates pressure, pressure means an enemy champion will have to answer that pressure, bring a jungler midlane means their jungle is free to invade and ward.
Now if you ace near midlane and the tower is still up, you have the choice, Drake or Tower? the answer is Tower. The only time Drake becomes massively impactful is the 5th Stack. Which takes sometime to get to.
Sometimes it is wise to level Tiger earlier than usual just for the extra tower damage.

If you are ahead as Udyr, teamfight as much as you can, however the problem begins when your team is behind. If your team is behind the other team it is wise to not teamfight as Udyr is not very strong in them. The reason for this is that he is easily kited with slows, snares stuns due to having no gapclosers. This is the point where you tell your team to turtle and you start pushing sidelanes for pressure.
When you see a 5 man mid push, try and get a tower before backing, as you will not be able to outpush 5 men, however you can make the best of a worst situation.
TIP: Do NOT Splitpush against Baron Buff.

When you are ahead as Udyr, you have the whole game in your hands. The best thing to do is to repeatedly gank lanes and push towers, it is important that you push towers once you dispose of the enemy's corpse. If you get 4 kills mid but do not touch a tower, you may be fed, but you are not applying map pressure, which is the whole point of playing Udyr. Do not be scared when the enemy jungler tries to defend the tower when you and your midlaner are pushing it, they can only do so much before you chunk the tower down.
When laning phase is over, you should have secured atleast 2 Dragons. You do not want to teamfight as it is your weakpoint. Only teamfight when you have a 1 item lead on the opposition.
When you splitpush make sure to utilise Phoenix Stance's Damage, as positioning yourself on the side of the wave, so that your Phoenix Stance hits all of them, can cause you to clear it 2 procs. You want to use Tiger on Turrets and Turtle / Bear, depending on which one has more points in as the more you level up an ability, the smaller the mana cost it. Try not to use Phoenix on towers as you can end up hitting an enemy champion and generating tower aggro.
TIP: ALWAYS pop into Turtle - Bear when you teamfight, as the shield lasts for 6 seconds and you will be able to block about 200 damage with it.

If you ever come to the point where you want to teamfight, it is crucial you activiate the right abilities. You generally want to use Bear Stance to stun everyone within a 200 unit radius before popping it into Phoenix, once you pop into Phoenix, make sure to keep moving in between each auto, to keep your distance. You want to peel for your ADC, so keep attacking their frontline, if you get low or start to get focused, pop bear into turtle and pray you can escape.
You only want to avoid this if their ADC / APC has no flash, in which case you can flash onto them and kill them, you will most likely die if the ADC positions well, but dying for an ADC is worth (Unless they're 0-5)

If you've got this far, thank you. This is my first guide and I am open to comments on how I can improve.