The start of chapel 12 is God telling Abram the call on his life. That God is going to bless him to make a great nation and even more importantly 12:3 "...in you all the families of the earth shall be blessed." God referring to Jesus Christ, Savior of the earth.
Abram went to Canaan just as God tells him, but when a famine comes he goes to Egypt. I read nothing that says God told him to. Abram also fears for his life and tells his wife to lie about who she really is. To me it seems Abram wasn't in God's will for his life and wasn't remembering what God promised him. How often do we do that also? We get caught up in the moment/situation and forget about the big picture. God keeps His promise even when it's us that cause our own mistakes. 12:3 "...him who dishonors you I will curse..." God curses the Pharaoh so he gives Abram his wife back. God protects and loves us no matter what.
Chapter 13 shares how God had blessed Abram's family so much the land where they were couldn't sustain all of it and strife was happening. To stop the strife they had to split ways. Strife isn't something you want in your life cause it's not healthy and if you are experiencing that with a person or people it's best to just split ways sometimes.
Lot picked what he believed to be the "best". Downfall to that was he settled to close to Sodom which, verse 13 says, "Now the men of Sodom were wicked, great sinners against the Lord." This probably contributed to him getting captured in the next chapter.
In chapter 14, after Abram gets Lot back he meets up with the king of Salem (the study notes says that it's possibly a shortened version of "Jerusalem") Melchizedek who was also a priest of God Most High. Verse 20, "And Abram gave him a tenth of everything." While giving had been mentioned before this is the first mention of a tithe.
Chapter 15 Abram questions God on what reward he will get due to the fact he was still childless. God tells him he will have his own son and his descendants will be as many as the stars in the sky. Verse 6, "Ad he believed the Lord, and he counted it to him as righteousness." This verse is quoted four times in the new testament. Faith is so important! It was Abram's faith in God that made him righteous not any deed/work!