What does the Bible say about praying for material blessings?
Many people have prayed for God to bless them materially. The Bible records some of those examples, but these moments are descriptive, not prescriptive. Just because Jacob (or any other person mentioned in scripture) prayed to be blessed in a certain way doesn't become a prescription for Christians today. God chose to bless people in different ways depending on His purposes. Sometimes God's answer matches a person's requests, sometimes His response is less than desired, and many times God's answer greatly exceeds our expectations.
In all cases, God accomplishes whatever He desires, and God's will never bends to the wishes of people. People may ask for whatever they desire, but we receive only what God desires to give us based on God's good and perfect nature and the counsel of His will. To teach that God always grants our requests for wealth and prosperity is a false, heretical teaching, and the false teachers who promulgate this view are often charlatans seeking to fleece their followers.
The truth of scripture is different, and we offer an in-depth teaching on God's response to prayer.