wanting to learn jungle
so i really wanna learn jungle. its the only role idk. i was thinking of using sejuani to learn. shes tanky and has good cc. what do you all think? also any tips for playing jungle? 
so i really wanna learn jungle. its the only role idk. i was thinking of using sejuani to learn. shes tanky and has good cc. what do you all think? also any tips for playing jungle? 
I'll try to give as much info as I can without creating a wall of text that you won't want to read.
Similar to lane, your Jungle gameplay will depend on the champion you pick.
For the purpose of examples, we'll use Sejuani. Sejuani is a tanky, CC heavy champion that is somewhat weak early game but scales pretty well into mid-lategame with her tankiness. This is pretty obvious if you've played her a few times.
With this information, we can gather that when you play Sejuani Jungle, it probably isn't a good idea to invade the enemy Jungle early. Although you have the potential to lockdown an enemy, you don't really have the damage to solo kill them.
But, because you have such great lockdown potential, and we know that you have trouble solokilling, it's fairly simple to see that Sejuani would excel in ganking. She can lockdown an enemy while a laner brings the damage.
When clearing with Sejuani, remember to remain cautious in your Jungle. Take the time prior to the game to analyze the enemy team comp. Do they have a Blitzcrank, Lee Sin, Shaco, Kindred, etc.? Expect an early invade. Do they have a Master Yi, Warwick, Shyvana, etc.? Use their time wasted farming to snowball your lanes early. The thing about this is that learning how to play against certain champs comes with experience. You'll learn what champs will play more aggressively or passively as you jungle against them.
Now, let's get into tips on ganking.
Before you gank a lane, take a look at you and your ally. As Sejuani, you bring quite a bit of CC. If your ally is, say, a Lulu mid, you might have trouble pulling off a gank early on because you lack damage. If you have someone with high damage, your CC will help them stick to the enemy and usually result in a kill.
After examining your kill potential, take a look at the enemy laner's positioning. As you approach the lane, do they start to play more cautiously? Chances are, you were spotted by a ward. Are they pushed up to your turret? Perfect opportunity to go for a kill. Much more time for you to damage the enemy before they reach safety.
Keep in mind, even if the gank will lack damage, a far-pushed enemy could still result in a kill if you have the time to damage them before they retreat.
Take a look at the enemy's escapes. Is the enemy laner a Leblanc, Fizz, Ezreal, etc.? They'll be a hard target to gank. The best way to pull one off is to wait for them to all-in your laner and burn their escapes while chasing. This leaves them vulnerable.
Where was the enemy jungler last seen? Could you and your laner pull off a 2v2 if they happen to show up? Make sure there is minimal risk of feeding a double kill to the enemy. Make sure the enemies are all visible in lane, or at least that they were a few seconds prior.
As for Map Awareness, you've probably experienced this already. If bot and mid are missing, they're probably at dragon. If top and mid are missing, chances are they're at herald. If top is suddenly MIA while ganking bot, they may have teleported to a ward. Keep this in mind when you play.
Is the enemy contesting dragon? Chances are, you need to smite perfectly. One thing a lot of people forget is that if the enemy jungler is a higher level than you, they'll have a stronger smite. Instead of focusing dragon, kill the enemy jungler first. If you know an enemy is lurking behind the wall to the pit, think about their skills. For example, if it's a Lucian, you can bodyblock his ultimate when he tries to steal.
Keep tabs on your smite timer so it's up whenever you go for an objective. If you're going to gank, try to save a smite if you have Stalker's or Skirmisher's.
Know when to take objectives. Successful gank on the enemy bot lane? Go for drag. Get kills on that gank? Tower then drag.
For your first clear, be wary. When taking the buff, ward over the wall to look for invades. If the enemy is a Lee for example, tell your teammates in advance you may need help. Most junglers can go for a gank at level 3 if they have enough health. If not, get enough gold for your smite upgrade as soon as possible then go back to looking for a gank.
As a jungler, you are responsible for creating pressure. When you gank, you may not always get a kill. If you force a flash on a champion with no other escapes, it forces them to play defensively so that your laner can farm more easily. If you take top tower, it gives your laner more freedom to roam. If the enemy mid and jungle gank bot, take mid tower in exchange. Your goal is to create more pressure than the enemy jungler and to impede the gameplay of the enemy laners. This is possible through more than just kills.
Wow. I lied. That was definitely a wall of text. Sorry broham... feel free to add me if you have any more questions or would like to play a few games.
Farm 6 ASAP and hit shit with R..
Jungling is less about how you play your champion and much more about how you play the game.
Nightblue3 and Stonewall008 do a pretty good job of teaching the basics of jungling (look them up on twitch/youtube). If you want a really easy champion, pick Warwick; you worry less about mechanics/surviving jungle clears and more about controlling the map. There's literally a flowchart on how to play Warwick (Is your ult up? Yes -> Gank. No -> Farm).
Personally I learned how to jungle on Udyr and Amumu; still play Amumu to this day. Sejuani is a lot like Amumu. No matter what, just pick a champion you like to play; you'll naturally become better since you'll actually play them more than a champion you hate
been jungling for several seasons. i would say it's most important to not fall behind in farm early and to hit 6 as quickly as possible for most junglers. farm your jungle efficiently by taking the most natural jungle paths and roughly knowing your jungle timers. if you're blue side for example, clear red side camps then blue side camps. once you take gromp, head back immediately to golem camp. only take the time to gank lanes that are really pushed up - in the time it takes you to gank, the opposing jungler probably clears 2 or 3 more camps, so your ganks have to result in kills or at the least blown summoners.
That's my advice: Learn to farm efficiently and only gank easy lanes. You'll learn nuances/how to improvise as you play more games - it takes time to learn when to countergank, when to sneak into lane bushes, etc.
Long live the Poro Rider, may she reign supreme.

I would suggest watching videos by Nightblue3, Stonewall008, TheOddOne, and foxdropLOL. They will typically provide a lot of useful tips while playing and you can often see or hear their decision process and some optimizations throughout the game.
Off the top of my head, some basic optimizations may be:
As far as ganking is concerned:
You will learn a lot through experience, but these tips should help you at the start.