daughter not listening

Okay my daughter will be two next month and her little sister will be here two weeks before her birthday. Well my almost two year old doesn't listen to me or her daddy. She will occasionally she is a good girl but recently she does stuff she knows she's not suppose to, she will stare at us while she's doing it to see if we are watching her. I've tried putting her in the corner when she doesn't listen but then she started putting herself there thinking it was funny. We've tried spanking her but it just breaks my heart when she gets spanked. So today when she did something she wasn't suppose to we put some of her toys up, well she goes and does it again not even ten minutes later so we put more of her toys up. I just feel so bad like I'm failing as a mom cause I can't get my daughter to listen to me. I know she's not even two yet it's gonna take time but I don't want to make excuses and then end up with a little brat I just feel like such a bad mom sometimes.