All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If this promise was just an intention and determination, and you did not utter the word of the promise with your tongue, then you are not required to do anything.
Nonetheless, if you uttered the promise and you broke it, then you uttered it and you broke it three times, then you have to pay three expiations according to the view of the majority of the scholars. But according to the Hanbali jurists, one expiation is sufficient for you. The view of the majority of scholars is better in order to be on the safe side, and this is the view we adopt here in Islamweb.
The expiation is to feed ten poor persons, 1.5 KG of rice for each poor person approximately.
If you provide lunch or dinner to the poor, or provide Iftaar meal to them to break their fast during Ramadan, then that is permissible according to view of many scholars, and this is the view chosen by Shaykh Al-Islam Ibn Taymiyyah .
If you provide two meals to the same people, it is better in order to be on the safe side, to provide them with lunch and dinner as per the view of many scholars, such as the Hanafi and the Maaliki Schools of jurisprudence; this is the view that we consider to be the preponderant one.
In feeding the people, you should make sure that the ones whom you feed are poor people who are deserving expiations, and it is not sufficient to feed other than the poor people in paying expiation.
For more benefit on the expiation for breaking a vow, please refer to Fatwa 102811.
Allah knows best.