What is the meaning of every line in sonnet 29?

When, in disgrace with fortune and men's eyes

In disgrace with fortune means down on your luck, to be disgraced with men's eyes means to be unpopular

I all alone beweep my outcast state

"Outcast" again suggests that he is unpopular. He is crying all alone about his "state", or how things are going with him.

And trouble deaf heaven with my bootless cries

We already know he's crying; not he says it's "bootless" which means it isn't doing any good. Saying that heaven is deaf suggests the same thing.

And look upon thyself and curse my fate

Somehow his unhappiness is related to the person he is writing the sonnet to ("thyself")

Wishing me like to one more rich in hope

Someone rich in hope has a lot to hope for--he wishes he were someone like that.

Desiring this man's art, and that man's scope

He's comparing himself unfavourably to other men: some have more art, or skill, and others have more scope or breadth of knowledge.

With what I most enjoy contented least

This is an inversion of the usual Word order. He means "least contented with what I most enjoy". So at the end of the octave we see that the writer is feeling pretty sorry for himself: he thinks he's unlucky and unpopular; he cries pointlessly, wishes he was some other guy, and can't enjoy what he usually enjoys the most.

Yet in these thoughts myself almost despising

But . . .

Haply I think on thee and then my state

Sometimes he thinks about the person the poem is addressed to and then . . .

Like to the lark at break of day arising

The lark is a bird that sings in the morning. Remember the argument between Romeo and Juliet? It was the lark (it's morning) that sang. No, it was the nightingale (it's night).

From sullen earth, sings hymns at heaven's gate

The lark "arises", that is, it flies up in the air and sings, leaving earth and flying into the heaven. So when he thinks on the person the poem is addressed to, his "state", like the lark, "arises", leaves the earth and flies free. He feels better.

For thy sweet love rememb'red such wealth brings

When he remembers the person's love, it brings "wealth", or many good things.

That then I scorn to change my state with kings.

He doesn't want to be some other guy any more, even if he is a king.