The Father saw the prodigal returning while he was 'yet a great way off'. The Most High chose His people in a past eternity and when the time comes for them to be converted in Time, as quick as a flash the Holy Spirit is at work in them.
The garment that was put on the prodigal speaks of the garment of Christ's righteousness which is put on His people. That garment was not complete until the Resurrection. When a person trusts in Christ by saving faith it is as if they put their arms into this garment.
The ring put on the prodigal's hand reminds us of power. Pharaoh put his ring on Joseph's finger although he had just been taken out of prison. A ring speaks of marriage and the Lord has his betrothed. A ring has no beginning and no end, just like eternity. The wandering evangelist, Finlay Munro said that to a lady who showed him the ring on her hand when he met on the moor of Lewis at the Ness shielings.
The shoes are important. Servants and the poor in Israel would not wear shoes. To have shoes meant you were in the house or in the family. It also means that the prodigal was to be obedient; for the Lord's people the shoes signify that they are to walk in a new direction, in the paths of holiness.
The fatted calf was kept for special occasions – family events or the various feasts in Israel. What it means is the best food available.