One way to look at this letter is as a spontaneous outpouring of praise to God. It certainly begins that way. But now we find that the praise consists of an enumeration of God's great gifts to his children, his blessings.
"Blessed (eulogētos, "blessed, praised") be the God and Father of our Lord Jesus Christ, who has blessed (eulogeō) us in Christ with all spiritual blessings (eulogia) in heavenly places." (1:3)
What we have here are the blessings come full circle, beginning with God ("who has blessed us “with every spiritual blessing") and finding their culmination in God ("blessed be the God and Father."). God blesses us graciously, without any compulsion -- just because he wants to. And we bless back, spontaneously, without any compulsion -- because we are thankful and love God.
Notice two things about these blessings:
They are "spiritual" (pneumatikos) blessings. These aren't mere physical or natural blessings, but blessings of our spirit by God's Spirit. The blessing of knowledge, the blessing of love, the blessing of mercy, the blessing of salvation -- the list goes on.
They are offered in the heavenly realm, not the earthly realm.
Ephesians introduces us to a phrase that we see throughout Paul's letters, but especially here -- "in Christ." In the first 14 verses of this Letter, the phrase (or its equivalent) occurs 11 times:
"The faithful in Christ Jesus" (vs. 1)
"Every spiritual blessing in Christ" (vs. 3)
"Chose us in him" (vs. 4)
"Freely given us in the One he loves" (vs. 6)
"In him we have redemption" (vs. 7)
"Which he purposed in Christ" (vs. 9)
"To gather up all things in him" (vs. 10, NRSV)
"In him we were also chosen" (vs. 11)
"The first to hope in Christ" (vs. 12)
"Included in Christ" (vs. 13a)
"Marked in him with a seal" (vs. 13b)
Elsewhere in Ephesians it is found at 1:20; 2:6-7, 10, 13; 3:6, 11, 21; and 4:32. The common Greek preposition en seems to be used in one of two senses in the phrase "in Christ" as found in Ephesians:
Local (locative): "in close association with." Often the phrase seems to carry the idea of "incorporation into Christ."
Instrumental: "Marker introducing means or instrument, with, by means of."
The preposition is used both ways in Ephesians, but I'm particularly intrigued by the local idea of incorporation into Christ, which I believe applies to most of the verses in our passage, especially in verse 11 where it talks about all creation being summed up in Christ as head. Likewise, in chapter 2 there are a remarkable number of compound verbs carrying the idea "together with," such as ""made alive with Christ" (2:5), "raised ... with Christ" (2:6a), "seated with him" (2:6b), etc. We are all "in Christ," part of him and he part of us. The primary idea of Ephesians is not Christ as the means by whom all these things come (though, of course, he is the means). Rather the primary idea is how we are joined with him in a spiritual sense. Our whole life is "in Christ." (See also Romans 5:12-19; 8:1; and 1 John 5:11-12.)