The question was asked concerning two people with limited income, one of whom cannot afford even a single candle for the Mitzvah of Chanukah candles, whereas the second has just enough money for all the candles. The basic obligation of Chanukah candles is to light but a single candle each night; the additional candles that we light are for the purpose of Hidur – enhancing the performance of the Mitzvah. The question thus arises in our case, should the second person give money to the first to allow him to purchase a single candle for the basic Mitzvah, if he himself will then not have enough money for all the Chanukah candles? In other words, should a person sacrifice his performance of the Mitzvah at the highest standard in order to allow his friend to fulfill the Mitzvah at the minimum level of performance?
The Magen Avraham (Rav Avraham Avli ben Chaim HaLevi Gombiner 1633-1683) writes that indeed, one should help his fellow Jew fulfill the essential obligation even if this necessitates sacrificing his own higher standard of the Mitzvahh's performance. Although this Halacha may not have direct, practical relevance nowadays, the underlying principle is an important one: a person should be prepared to help others perform Mitzvot at the minimum level, even at the expense of his own performance at the highest standard.
Another issue addressed by Halacha concerns a person who can afford either Shabbat candles or Chanukah candles, but not both. In such a case, Shabbat candles take precedence over Chanukah candles, because the purpose of Shabbat candles is to provide light in the home to enhance Shalom Bayit – a sense of domestic peace and serenity – which overrides the obligation of Chanukah candles. If, however, a person already has light in his home – even a single light bulb – then this light suffices for the obligation of Shabbat candles. Therefore, if a person has a light in his home but cannot afford candles for Chanukah and Shabbat candles, he should light Chanukah candles, since he already fulfills the obligation of Shabbat candles with the light in his home.
Summary: One should give money to a poor person to buy a single candle for Chanukah, even if as a result he will not have enough money to light all the Chanukah candles. If one cannot afford both Shabbat and Chanukah candles, Shabbat candles take precedence; if he already has a light in his home, even just a single light bulb, then Chanukah candles take precedence, since he can fulfill the Mitzvah of Shabbat candles with the light in his home.