Question about pressed powder and concealer?

I'm 13 and kind of inexperienced in the make up department. My sister bought me a Covergirl pressed powder because I've started getting a few pimples and such on my forehead. I haven't opened it yet so I don't know if its heavy or not, but are Covergirl pressed powders good for coverage? For anyone who owns one, is it a heavy powder? The package says that the primary use is for coverage but "for best results, use with foundation or concealer." will it still work if i dont have any foundation or concealer? how soon will it rub off? i only wanted to buy a decent coverup so its okay if its not great. thanks!