Revelation 4:11 "Thou art worthy, O Lord, to receive glory and honour and power: for thou hast created all things, and for thy pleasure they are and were created."
It is very clear we are created for the pleasure of God. We please Him by believing in Him.
Hebrews 11:6 "But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him."
God desires that we trust Him and take Him at His Word. Through our relationship with Him and obedience to His Word, we demonstrate that we believe that He is and that He has our best interest at heart. When we live in accordance with this, we both please Him and bring glory to His name. This is the chief purpose of mankind.