Having trouble with Nature's Prophet, can anybody give me any tips?

So recently I have been looking into Nature's prophet and he looks extremely fun to play, so I practiced him in a few bot games as jungling then went into two real games with him. We lost both of them and I ended up going 5/9 in both of them, I feel like I am a major part of why we lost the games, I struggle with positioning in team fights and when to TP in for a gank and such. Any help would be appreciated.