How we cite our quotes: (Act.Scene.Line)
Quote #1
Could I be one of their flatt'ring panders, I would hang on
their ears like a horse-leech till I were full, and then drop
off. […] Who would rely upon these miserable
dependences, in expectation to be advanced tomorrow?
[…] There are rewards for hawks and dogs when they
have done us service, but for a soldier that hazards his
limbs in battle, nothing but a kind of geometry is his last
supportation. (1.1.54-60)
Bosola has just indulged in one of his favorite hobbies: talking smack about how bad princes and courtiers are. His follow-up to this review of the brothers? "Gee, I wish I could serve them." One of the central contradictions of Bosola's character is that he both hates the screwed up social system of the court, but also wants to be a part of it. He mocks those "who would rely upon these miserable dependences in expectation to be advanced," but shortly after he makes this speech he becomes Ferdinand's spy.
Quote #2
I am your creature. (1.1.280)
Bosola has just agreed to be Ferdinand's intelligencer. Think about this word, "creature": these days our minds tend to automatically think "animal," but more literally it means "something created." Go check out Quote #2 in Power to see Ferdinand's statement that he thinks his courtiers should be his "touchwood"—he wants to duplicate himself among his courtiers, instead of have a reciprocal relationship with them. Here, Bosola 2.0: Spy Edition is being created by entering into the service of Ferdinand, and belongs to him.
Quote #3
This goodly roof of yours is too low built,
I cannot stand upright in't, nor discourse,
Without I raise it higher. Raise yourself,
Or if you please, my hand to help you […] (1.1.408-411)
The Duchess wants to marry Antonio, but she can't do it while he's kneeling in front of her as her employee. To have a real, equal romantic relationship with him the Duchess has to hike Antonio up to her level socially, which she achieves by marrying him.
This scene also prominently features the Duchess literally raising up her steward with her hand, presenting Antonio's social ascension not just as a result of a noble woman marrying a socially inferior man, but, importantly, as a prince showing favor to a servant. For more on raising and kneeling, check out the "Symbolism, Imagery, Allegory" section.