I wanna look good. Help?

Okay, so here it goes. I'm a girl I'm 15. And I'm a nice person. I really really just need to know how to look good. I don't seem to be charming but i could sometimes have a good sense of humor. I need to lose weight but i'm not really that fat, i just wanna look skinny. Especially the thighs and legs (it runs in the family) And i don't have swag. What i mean by "swag" is (please dont remember justin bieber by this or something) I don't seem to look good in my actions and in the gestures i do. When I clap my hands i seem to look lame. When i try to feel the rhythm of music and try to sway to it i really look lame lame lame! and when i dance i look soo sooo bad. It's mostly about dancing, yeah lol. And when i dress up people just seem to dress up better than me. I'm simple with dressing up, denim shorts v necks or crop shirts. And i don't know how to control my tone when i talk. i just seem so lame and i wanna be cool. I wanna be confident and cool. And i also want to be charming. I need help, with each of the problems i just stated. please do help me. You will be a great impact in my life and i'd remember you someday when i get famous ;)