Greetings (1-2): Paul writes to the Ephesian[1] believers, whom he calls holy.[2] He, moreover, calls them faithful,[3] which seems connected to the good report about them (1:15). To these faithful saints, then, he sends his warm greetings.
Every Blessing (3): The eternal God of the universe[4] has blessed us, not with just some of His blessings, but every spiritual blessing (every single one of them!). And these are spiritual blessings, not the lackluster and transient quasi-blessings belonging to this cursed world.[5] These belong to "the heavenly places." These are the best of God's blessings! And these are all inextricably tied to the Lord Jesus Christ.[6] Separate from Him, God would have given us no blessing. Christ is the treasure in whom we have every heavenly treasure.
Election (4a): God's blessings began with His divine election in eternity past. God chose us "before the foundation of the world."[7] Before the beginning of the world, before the heavens and the earth, God selected us for His blessing! Now, the purpose of this election was that we'd be "holy and blameless", i.e., conformed to God's own holy character (4:24; Heb. 12:10; 1 John 3:2-3). And this was all done, not for our self-aggrandizement or vainglory, but for Him. We were chosen to be a holy spectacle "before Him," for His own pleasure!
[1] Evidence shows that "at Ephesus" was omitted in manuscripts very early in church history. But, since this letter was intended for a particular audience (cf. 1:15; 6:21), the location is best retained as per NASB.
[2] "Saints" is simply the adjective "holy [ha-gi-os (ἅγιος)]" or "set apart." This is literally "holy/set apart ones."
[3] "Faithful" stands out because Paul rarely addresses his recipients as this, only here and Col. 1:2.
[4] Paul considers the eternal Creator of the "world [kos-mos (κόσμος)]" (1:4)! Cf. Psalm 90:2; John 17:5, 24.
[5] These blessings are incomparably better than the here and now (cf. 1 Cor. 15:52-53; 1 Pet. 1:4; Rev. 22:3-5).
[6] Christ is the lynchpin for all the blessings (1:3-14). He alone can give eternal life (John 10:27-28; Rev. 3:5).
[7] Scripture affirms this pre-creation plan of salvation which God has for His elect. Cf. 2 Tim. 1:9; Rev. 13:8.