getting photos from my camera roll to my library without duplicating

i understand the difference between camera roll and photo library. the last time i synced, i transferred pics to a folder in my computer and chose to sync that folder. the problem is that now i have my camera roll, photo library and that folder from my computer on my phone with the library and the folder just duplicating (the exact same pictures). i'm missing something and don't understand how to sync pictures properly...like i'm just not picking a correct option. i want to be able to more efficiently use the space on my phone...get stuff off my camera roll and have my most important pics on my phone without duplicating. i get that it's easy with iphoto and a mac, but i'm having a hard time finding direction for those of us using windows. ANY help would be much appreciated!