How do I know whether I should pick a strong early ganker or a powerfarm jungle champion for a game?
Like if I pick Warwick in the wrong scenario, my team will have no towers before i even reach level 6. But if I pick Pantheon in the wrong situation the enemy team will just play super safe til I fall off late game.
How do I know what to pick in what team comps and matchups?
Generally, you want to pick a jungler that makes up for team weaknesses (damage, tankiness, peel, etc). In your case, however, it's a bit different. Look at who you're up against, and try to think about how the champ will act (Riven players are really aggressive, and therefore susceptible to ganks, Vayne's going to play a farm-based safe lane, etc). From there, find a jungler that can capitalize on it. If they're going to be really safe, farming their lanes and poking to clear waves, pick a farmer and stack that devourer. If they've got aggressive lanes, be prepared to gank, and gank, and gank.
There's my thoughts, anyway. I don't play Jungle too much, so I'm just speaking from the limited knowledge I have. If you want tips on how to pick your jungler, a youtuber named Stonewall008 is making a series right now about how to pick a jungler. The guy also knows a lot about the jungler role and the game in general (he's been playing since Season 0), so it's a good place to find tips.
Hope I helped!
pick someone who is both a gank and a farm jungler ............... and can do both depending on what your team needs
https://www.youtube.com/watch?v=i0aVqMsHx18 This should answer your question pretty well.
