what felt the easiest for me was annie. she was an extremely easy champion to learn. easy last hitting mechanics, simple passive skill, easy combo. played to perfection she is very hard, but the basics are easy. also fizz was my 2nd champ (warwick was my first) and i found him very easy. only one skill shot, very forgiving last hitting mechanism because of w passive (first tick is immidietly so you basically get increased damage on auto attacks even if you dont activate it), easy combo, and is really fun to play.i had tons of fun playing fizz. darius is considered easy, but i dont know, i never played him. karthus, veigar, kassadin and orianna are out of the question - very hard champs (atleast for me, although i do play them).
sivir is a very easy champ. you right click stuff, then you w and continue to right click stuff, and if stuff are running too fast, press R and continue right clicking stuff that are not running so fast anymore.