Statistics are saying that in Iron Elo his winrate is slightly above 50%. However note that his winrates are falling down significantly with each ELO you climb up. At Diamond his winrate falls down below 48% and in Grandmaster his winrate is actually only 43.74% which is extremely low number. In Challanger his winrate comes back to average of 50%.
Also keep in mind that he is up to receive a buff in patch 10.18 so numbers may change.
Overall in my opinion he is not the worst pick for climbing, however there are other much better junglers you can select instead of him. For example Rammus has over 56% winrate in Iron ELO and even though his numbers are also descending with each ELO you climb, it falls below 50% only post Diamond. Warwick, Jax or Amumu are also very great while being overall easy to learn.
He's certainly good in low elo, however, a drawback that comes with playing Jarvan in any elo is that his kit is great, but functions at its peak with competent teammates, so you can certainly play him in low elo, but you might want a duo, as was said earlier.
If he's good in higher elo, then it should be super in the low elo, only problem I could see is you might need a duo, because I don't know how much people actually care about what the next person picks to complement/be aware of how to fully utilise the pick.
Also keep in mind that he is up to receive a buff in patch 10.18 so numbers may change.
Overall in my opinion he is not the worst pick for climbing, however there are other much better junglers you can select instead of him. For example Rammus has over 56% winrate in Iron ELO and even though his numbers are also descending with each ELO you climb, it falls below 50% only post Diamond. Warwick, Jax or Amumu are also very great while being overall easy to learn.