There are many reasons to pray and many benefits from prayer. However, the most important reason is to directly connect to God through the Holy Spirit. Prayer is the only significant way to develop and grow in your relationship with the Lord.
When I first started praying, I used a transactional approach. I had a laundry list of things that I wanted. As pure as my desires were, they were just that, "my desires". Even though I asked for forgiveness of my sins and prayed for good things to happen that should have been pleasing to God, I was missing a key ingredient.
I was not willing to SURRENDER. I capitalize this word because it is so important. Until I was willing to yield to God's will in my life, my prayer life and walk with God was incomplete. I think that surrendering to His will is the most difficult thing I have ever done. It is also the most rewarding experience I have ever had.
I pray that you will also ask the Holy Spririt into your life to guide and direct you daily.
There are many great books on prayer, however, I would suggest reading The Purpose Driven Life by Rick Warren as a starting point to get a larger perspective on why prayer is so important.