Shulchan Arukh, Orach Chayim 678/שולחן ערוך·אורח חיים תער״ח

1Someone who cannot afford both Chanukah candles and Shabbat candles should buy a Shabbat candle, for the sake of tranquility in his household (see above Siman 263:3); and if he has money for a Shabbat candle, but not enough for a Chanukah candle and kiddush wine, he should be a Chanukah candle, to publicize the miracle. Rema: And such is the ruling, that a Chanukah candle takes preference over wine for Havdala, and see above Siman 296:5).