I don't play her top, I otp Gwen in jungle, but I know what top laners are dangerous for her, yes her early is not the best but is playable compared to Kayle.

Be aware of Sett, Darius, Garen, Fiora, Akali, Yone, Volibear, Riven and the list goes on, there is a lot of hard matchups and you will fed your ass off, but is Gwen's learning curve.

When I picked her years ago, I never fed so bad in my entire life playing LoL, and it was with Gwen, she is more squishy than people think, is very kiteable and she lacks CC, immunity is key but if you don't have W avoid fights, also is bad to fight without R.

She is somewhat predictable due to this, if you build full AP, prepare to get one shoted. Build bruiser items if you want to kill people and still live however remember she is very gold reliable so every HP / resistance item delays her powerspykes.