but one thing to do is, everytime you encounter a new champion, read about their abilities or maybe even see videos on Youtube. You need to know what the other champions can do, their safe distance, what spells to they usually max, etc. Once you estabilish a wide database, you'll feed less and win more games.
Also, pick a champion you enjoy playing and main it. When you're just starting, you'll need to be able to survive on your own, don't rely on your team to save you, so pick a champion with good mobility / escape.
what's your name on LoL?