Just say: " Poproszę..." and the brand of cigarettes you want. You may need to add which type, like "czerwone" (red) or "niebieskie" (blue). For light, we say:" Lajty" :)
Shopkeeper may say " Coś jeszcze?" (anything else) , or " To wszystko?" (Is that all?) but that's about it.
Also bear in mind, that most of the cigarettes brands are English words, and since most of Polish people are unfamiliar with the correct pronunciation, they just come up with the polonized verison: "Elemy" would be L&M, " simple polish accented Malboro will be Marlboro and so on.
The shopkeepers especially in a kiosk stand or in a small corner stone, will not now know any English, so just smile, say" Poproszę" be ready to point and you will be fine. Good luck!