Avraham begins Parshas Lech Lecha as the wanderer, indeed the Parsha itself is named after the act of exile. Thus far both preceding Parshas, Bereishis and Noach, involved a forced exile, Adam from Gan Eden and Noach from the earth itself. Yet Avraham's exile is unique for it foreshadows a new sort of exile, not from a better place to a worse one as with Adam and not a salvation from destruction to dispossession as with Noach, but an exile from a worse place to a better one, thus reversing the path of mankind up until that day. That long exile that his descendants, the Jewish people would suffer, is still that exile with a final return to a better place than the one we left. No matter what travails we suffer in the journey, we are still Avraham's children traveling through foreign lands on the way home.
Avraham's travails however usher in new problems. When Avraham reaches Egypt, he passes off Sarah as his sister, which leaves her under the authority of Pharaoh. He then accepts gifts and presents from the Egyptian nobility and Pharaoh himself. The disastrous consequences of this are twofold.
Firstly the birth of Yishmael, the son of an Egyptian maidservant or princess, that occurs when Sarah reverses the process by which Avraham put her under the power of Egyptian men by giving him an Egyptian woman. The result is Yishmael, a bandit and rogue who goes on to persecute her own son.
Secondly, the gifts Avraham takes creates an obligation in his descendants that cause them to be banished to slavery in Egypt. This results in G-d's vision informing Avraham that his descendants are to be slaves for centuries, because in having allowed the Egyptians to enrich him, the Jews could only properly be considered blessed by G-d when they discarded all of the material possessions provided by Egypt and reacquired them only through the force of divine power.
And thus the Jews became slaves, dispossessed and property themselves and through the progress of G-d's miracles, were the Egyptians sufficiently intimidated as to agree to the "loans" of property solicited by the Jews at G-d's explicit command. Why did G-d command Moshe to tell the Jews to take out these loans? In order to fully redeem the Jewish people, body and soul. The new riches that they emerged with after they left Egypt and the Egyptians pursued their human and physical "property" and washed up on the shore after being drowned by Divine Intervention were given directly through the power of G-d and not the power of man.
Thus Avraham had learned his lesson after learning that the Jews would be enslaved for centuries and rejected the "gifts" of the King of Sdom, for once the King offered it as gift, it was no longer a Divine Conquest, of the sort from which Avraham had offered his Masser. Had Avraham done it, the Jews would have fallen under the power of Sdom. Instead Sdom was destroyed rather than enduring throughout the centuries and millennia as Egypt did. When Avraham prayed for Sdom, he prayed that it be protected in the name of anyone righteous living there. He did not however pray in the merit that Sdom had done anything for him. Had they done so, it would have been a merit for them.
When Avraham and Sara learn that they are to have children, both Avraham and Sara laugh and view it skeptically. As a Mida Keneged Mida for laughing skeptically over a divine blessing that did come true, they were forced to mourn over a dark divine command that did not come true, namely the sacrifice of Yitzchak. Had they truly laughed with joy, this would not have been necessary. Instead as a consequence of not believing the miracle until they saw it with their own eyes, at the Akedah Yitzchak grew blind and was unable to believe the evil of Esav and could be fooled by Yaakov.
Unlike Adam, Noach and Avraham and Yaakov and Yosef and Moshe, Yitzchak was never exiled. Exile for great men is meant to transform them and transform the world or punish them but Yitzchak was not meant to transform the world and he did not deserve punishment. He was simply perfect but his perfection could not reach others. He passed along the Mesorah unchanged but for the addition of Mincha. Mincha is the border between day and night, between Avraham who brought light to the world and Yaakov whose descendants went down into darkness. The Mincha pleases G-d. It also relates to Menucha, and of Menachem, comfort Yitzchak's life was generally at rest compared to the other Avot. Sandwiched between exiles, Yitzchak bore the truth of G-d and yet was deceived, for it is hardship that schools us to recognizing evil.
Avraham took far too long to recognize the evil in Yishmael, yet when he did, he acted decisively. But Yitzchak remained blind too long to the evil in Esav. It was only Yaakov whose life was mostly spent in exile, who could properly rebuke his sons on his deathbed. People are not born perfected. Hardship tests them and enables them to see more clearly the good from the bad.