Best to stick with the Scriptures. Let them tell you what "begotten" means, and don't go any further than the Scriptures go.
"Of one Being (homoousios) with the Father" is not Scriptural, as many protested at the time the creed was adopted by the council.
When Jesus said, "I and my Father are One" (John 10:30), Jesus was here in mortality and God the Father was in heaven. In John 17:20-21, Jesus explains how They are One. He prays that all believers may be one as They are, so "one" does not mean the number one, but perfect unity in all respects -- heart, mind, purpose, thought, action, etc.
In other places Jesus prays to God the Father, says "the Father is greater than I", and "neither came I of myself, but he sent me", all inconsistent with the notion of one Being or substance.
>> We believe in the Holy Spirit ... who proceeds from the Father (and the Son).
John 8:42 Jesus said unto them, If God were your Father, ye would love me: for I proceeded forth and came from God; neither came I of myself, but he sent me.
John 15:26 But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:
I (a Latter-Day Saint) will have to agree with the Eastern Orthodox that "proceedeth from the Father" comes right out of the above verse, with no "and the Son". "Proceedeth from", in my opinion, is another way of saying "is sent by" or "was sent by", and in the above we see that Jesus sends the Spirit (from the Father), so the Roman Catholics have a point also.
Best just to stick to the Scriptures, in my opinion, and not worry about creeds.
ekporeuomai (Strong's 1607) {ek-por-yoo'-om-ahee}
1) to go forth, go out, depart
... so I should say "proceed" is what you do when you are "sent" from the presence of God the Father to minister to those on earth.