So what was elected by God is first the Gospel Message as means to save peoples, and also Body of Christ was elected as a whole and depending on how we respond to message determines if elected into Body or not?
I'm not sure I understand your question, but allow me to try and take one more stab at explaining my view in the most simple way I know how.
1. We believe men are saved (credited as righteous/justified) through their faith in God and His revelation. "Abraham believed and it was credited to him as righteousness." "By grace, through faith."
2. The gospel is the special revelation of God by which He makes appeal to all mankind: "Be reconciled to God." (2 Cor 5)
3. WHOSOEVER believes that message (a divine revelation from God) will be saved by grace through faith.
4. The Jews had been the recipients of God's special revelation for generations, they were known as the elect of God (Rm 10:21). This revelation was made through the prophets and scriptures by which the Jews as a group were offered entrance into covenant with God. But individually the Jew had to fulfill his part of the covenant (i.e. circumcision). So, you have Israel (corporately speaking) being granted the OPPORTUNITY to enter covenant with God, but the JEW (individually speaking) had to meet certain requirements. Israel (corporately speaking) rejected this revelation and was unwilling to follow God in faith (Matt 23:37).
5. Enter Christ, the gospel, the apostles, the church...
"Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin. But now a righteousness from God, apart from law, has been made known, to which the Law and the Prophets testify. This righteousness from God comes through faith in Jesus Christ to all who believe."
6. This gospel was sent to the Jews first, but they rejected it (corporately speaking). They were being hardened, or blinded from the gospel truth (John 12:39-41; Acts 28; Mark 4; Matt 13; Rom 11, etc). They were being "cut off" from the means of salvation, the divine revelation of God. They used to be the elect ones who received the special revelation by which they could individually enter into covenant with God, but now they were being cut off from that source. (God did this to ensure the crucifixion and ensure the ingrafting of the Gentiles into the church)
7. So, once the Jews rejected the gospel it was sent to the Gentiles, because "they will listen." (Acts 28:28) They are being "grafted in" and thus granted the opportunity to enter into covenant with God. God is showing mercy to the Gentiles (corporately) by granting them repentance unto life, but just like with the OT covenant, there was a condition for the individual: FAITH. (God's acceptance of the non-Jew was the "mystery" being revealed for the first time in that day. It was God's predetermined plan all along to graft them in, they were foreknown from the beginning. But it was just being made known to the world at this time)
8. Within all this God reserved for himself out of Israel a remnant to carry the gospel message to the rest of the world. He individually chose them for "noble purposes" while leaving the rest in their hardened condition for "common use." (Rm 9). Paul is an example of one of these individuals chosen specifically by God to be a divinely appointed messenger to the nations.
In summary: God elected Israel corporately to reveal himself to and through, but the individual Jew was still responsible for his part of the covenant in order to be considered in covenant with God. God elected certain individuals from Israel to carry the message of good news to the rest of the world. God elected the Gentiles to be grafted in and thus receive this divine revelation, by which whosoever (individually) might believe and be saved.
I don't think I can make it any more clear, but feel free to ask questions if this doesn't answer all your questions.