I played for a while, and came back. I have 4 good friends who play and we want to form a team. I enjoy playing Rengar, but I am curious if he is viable as a jungler currently. I jungled SOME when I played before so I shouldn't have an issue getting back into it.

TlR Is learning jungle with rengar worth it?

Yes he is very much worth it and is a great jungler when played properly. Him and maokai were my main junglers in carrying myself up to gold rating on my main. The key is learning too jungle with him properly.
If you have any questions feel free to add this account.