The number of expiations depends on the number of oaths

It is makrooh to be careless in swearing aaths, because Allaah says (interpretation of the meaning): 

“And (O Muhammad) obey you not everyone Hallaaf Maheen (the one who swears much and is a liar or is worthless)”

[al-Qalam 68:10]

This indicates that the one who swears oaths a great deal is to be criticized, so try not to swear oaths too much, out of respect towards Allaah and so as to protect your oaths. 

You should note that swearing oaths a great deal for everything, minor or major, leads to weakening the value of oaths and vows in people’s eyes, and there is no guarantee that this will not lead to making false oaths, and it also indicate that one does not fear Allaah completely. 

With regard to the oath that you have sworn, they may be interpreted in one of two ways: 

1 – When you swore the oath you meant to swear an oath, in whole or in part, i.e., you meant to swear a binding oath. In this case you have to offer kafaarat yameen. A binding oath is one which a person swears concerning something in the future, that he will do something or not do something. 

2 – When you swore the oath you did not mean to swear an oath as such. This comes under the heading of idle oaths. The scholars differed as to the precise definition of idle oaths (laghw al-yameen). The most correct view is that the idle oath includes the following: 

1-That which the speaker utters unintentionally, such as when a man says, “No, by Allaah, I will never go” or “Yes, by Allaah, I will go.” This is the view of the Shaafa’is and Hanbalis.

2-When a person utters an oath thinking that he is speaking the truth, then he realizes that it was not true. This is the view of the Hanbalis.

3-Shaykh al-Islam added to the definition of an idle oath cases where the one who swears the oath thinks that the one concerning whom it is sworn will not go against him, then he does go against him. By the same token a person does not break his oath if he swore that another person would do something by way of honouring him, not by way of compelling him. He said: Because it is like a command; a command is not binding if it is understood to be by way of honouring, because the Prophet (peace and blessings of Allaah be upon him) commanded Abu Bakr to stand in the row but he did not stand. See Majmoo’at al-Rasaa’il al-Fiqhiyyah by Shaykh Khaalid al-Mushayqih, p. 234.

Based on the above, if all or some of your oaths were binding, then you have to offer kafaarat yameen, but do you have to offer it once or several times? That depends on the content of the oath. If all your oaths had to do with the same thing, then you have to offer expiation only once. But if you swore oaths concerning a number of things, such as saying, “By Allaah, I will not eat today” and “By Allaah, I will not drink today” and “By Allaah, I will not travel today”, then you have to offer expiation for each of these things if you did it. If you ate and drank and travelled then you have to offer three expiations. If you swore one oath concerning a number of things, such as if you said, “By Allaah, I will not eat or drink or travel,” then you have to offer expiation once for doing one or all of these things. (op. cit., p. 266). 

But if all or some of your oaths were idle oaths, then the majority of scholars have stated that no expiation is required for breaking an idle oath, because Allaah says (interpretation of the meaning): 

“Allaah will not call you to account for that which is unintentional in your oaths”
[al-Baqarah 2:225] 

And Allaah knows best. 

See also questions no. 45676, 34730.