Siman 678
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א מִי שֶׁאֵין יָדוֹ מַשֶּׂגֶת לִקְנוֹת נֵר חֲנֻכָּה וְנֵר שַׁבָּת, יִקְנֶה נֵר שַׁבָּת מִפְּנֵי שְׁלוֹם בֵּיתוֹ (וְעַיֵּן לְעֵיל סי' רס"ג סָעִיף ג'); וְאִם יֵשׁ לוֹ לְשֶׁל שַׁבָּת וְאֵין לוֹ לְנֵר חֲנֻכָּה וּלְיַיִן לְקִדּוּשׁ הַיּוֹם, יִקְנֶה לְנֵר חֲנֻכָּה, מִשּׁוּם פִּרְסוּמֵי נִסָא. הַגָּה: וְהוּא הַדִּין נֵר חֲנֻכָּה קוֹדֵם לְיֵין הַבְדָּלָה, וְעַיֵּן לְעֵיל סי' רצ"ו סָעִיף ה'.
1 Someone 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).