How much do looks really matter and what are some general pointers on how to get a girlfriend?

When I keep asking people advice about talking to girls or ever having a girlfriend, I immediately am told to change my appearance, the way I dress, and even the backpack I have (it's a rolling suitcase). I'm a college student, but how much do looks really matter? I'm not filthy (quite the opposite), shave every day, always dress relatively nicely, and drive relatively good car. These comments really affect my confidence (i'm horribly unconfident and have a low self esteem), make me feel that I will have to act completely artificially which almost seems to kill the entire purpose, and undermine me so much I don't know what to do (I've never had a girlfriend). I want to experience a relationship not for ual purposes, but for everything else about it, but I am hopelessly lost and don't think it will ever happen. Please help.