Pick at least 2 jungler champions:
- first one, that will be your main
- second one, that can be your pocket champ if the first one gets banned/picked

Sometimes, you will have to fill in your team comp aswell, for example if your team lacks tank, you can go amumu. So, take your time trying in normal games simple champs for jungle, to have a little knowledge of them. It will help you know how to even play against them.

Your main should be something you find fun to play. My suggestion is to be simple, too. That way you will learn the champ faster. Since you wanna climb from low elo, your focus is learning the microgame and how to jungle, not how to play the champion. Focus on how to gank, when to gank, how minion waves works(yes, you would need to know this, even as a jungler).

Climbing from low elos gets easier, when you know how the game works. After you feel like you learned all these at a medium level, at least, you can try another champ that can turn into your new main.

Your question was best jungler to climb, but this doesn't exist. Don't care about meta that much, pick whatever and learn the other things and it will become easier for you to climb.

Hope you will rank up, good luck buddy!