Held by this electric self out of the pride of which I utter poems, (7)
The speaker has a sense, here, of why he writes poems. It's pride in the electricity that flows through him. The speaker has a certain kind of energy that allows him to write, and it's this pride that "holds" him and allows him to experience the world the way he does.
I too but signify at the utmost a little wash'd-up drift, (22)
The speaker starts to identify with the trash on the beach and the things brought in by the drifting tide. He's just a by-product of the oceans of life; whatever created him is part of something larger, he says, and he knows that he's just a small piece of the whole. Or perhaps he just thinks that he isn't worth much. Either way, he identifies pretty strongly with the trash on the beach.
Aware now that amid all that blab whose echoes recoil upon me I have not once had the least idea who or what I am, (27)
Realizing you have no idea who you really are is really no fun. All the things he has ever said revisit him now, and they seem as silly as "blab." They "recoil" against him like waves, too, adding to the unpleasantness. It's safe to say that he's deep in an existential crisis.
But that before all my arrogant poems the real Me stands yet untouch'd, untold, altogether unreach'd, (28)
Who is the "real" you? Is it the one that walks and talks to other people, or the one that no one has seen? In this line, the speaker is having trouble reconciling the two sides of himself. He even thinks of his poems as "arrogant." Fortunately for him, there seems to be a "real" self out there waiting, "untouched." The trick is just figuring out how to find it.
I mean tenderly by you and all, I gather for myself and for this phantom looking down where we lead, and following me and mine. (55-56)
Here, the speaker is not only unified with himself, but with all of us, even with the "phantom" who looks down on us from above. He gathers all this sentiment of unity for all of us, and shares it in the poem. And he does so "tenderly." The tone of existential despair and isolation has given way to peace, here, as the speaker finds his true identity by considering how united we all are.