If you don't even know names, you probably are WAY too early to be worrying about "mastering" a character.
Learn what all the characters do first, then figure out what role you like the most, then learn some characters from that role, THEN worry about perfecting a single one.
If you just tunnel-vision on a single character without learning the game as a whole first, 1) You'll be a liability to your team and that's never fun and 2) You'll only get good at the basic mechanics of a single character while playing a strategy game, which means you'll lock yourself down to the "I can beat my lane but can't win games" situation that so many on this forum whine about.
Lastly if you're one of those "whose the best character in the game so I can play them and feel good about myself?" types everyone hates as a kid, you're going to run into some problems here, sorry.
As for whether Nidalee (that's her name) is a good pick, that wildly depends. If you're asking "Is this character overpowered so I can abuse them", then I can't/won't help with that, but if you're asking "is this character a good pick for me?" you'll have to give some more background, like what types of characters you like playing in other games, or how you liked playing Teemo, etc.
Have to reiterate that if you're on the forums asking "Hey guys what's overpowered I wanna learn that first so I can win", not only are you going to get a billion answers (most of which are wrong), but you should also just stop playing while you're ahead: That's an absolutely god-awful mentality to have.