salm 16:8-11 is clearly a Messianic prophecy (Acts 2:25-30), but what about the first 7 verses of Psalm 16? Well, I'm not sure how it all fits together, but of those 7 verses, I confess that verses 2 & 3 are the hardest to interpret. If in Psalm 16:2 David was decrying his own goodness compared to the goodness of God, fine. But, where does the rest of the sentence fit in? David's goodness did extend to the saints around him? I'm suddenly lost.
Perhaps the verses are a reference to the benefit of Christ's earthly service and ministry. There was no lack in the Father that He would need to have additional goodness contributed in His direction. The Father is the spring, reservoir and source of all goodness, not a needy recipient of it. The plan of redemption is aimed squarely at the elect of God (Acts 13:48). We are the needy ones. Of course, there are many others who are needy also, but their willingness to be distracted by the appeal of petty gods prevents the one true God from effectively extending to them the gospel goodness which could connect them to Him (Matthew 7:23).
Concerning the rest of the Psalm: in verses 1 & 5 we can see both David's and Jesus' dependence upon the Father. Verse 6 reminds us of the heavenly inheritance which we share as sons of God (Romans 8:17 & Ephesians 1:3 & 2:6). Verse 7 speaks then of the guidance and direction which Christ had... and which we have also (Matthew 4:1, Mark 2:8 & Romans 8:14).