How can one atone for numerous unfulfilled vows and false oaths, so as to expiate their sins?

A Muslim must fulfill his vows and safeguard his oaths. Whoever vows obedience to Allah, let him obey Him. Whoever swears an oath, let him safeguard it. All vows must be fulfilled, and expiation must be paid for every oath that is broken, unless the multiple oaths are on a single matter to emphasize the oath, in which case only one expiation is due. Caution must be exercised in giving out expiations until one is reasonably certain of clearing their conscience, and similarly with vows. One must hasten to sincere repentance from lying and swearing by it, for swearing a false oath is a "Ghamoos oath" (a deeply sinful oath) and a major sin. It is more prudent to pay expiation for it to avoid scholarly disagreement.