It is the day of the Carnival, and Belville and Willmore have just met a pair of gypsies (who are actually regular women named Florinda and Hellena in disguise). Willmore, who is an unapologetic sexual libertine, is captivated by Hellena's wit and cannot stop thinking about her. Falling in love is presumably a new experience for him and one that he does not like too much.
...A Pox on't, I cannot get her out of my Head: Pray Heaven, if ever I do see her again, she prove damnably ugly, that I may fortifie my self against her Tongue.
Have a care of Love, for o' my conscience she was not of a quality to give thee any hopes.
Pox on 'em, why do they draw a Man in then? She has play'd with my Heart so, that 'twill never lye still, till I have met with some kind Wench, that will play the Game out with me— Oh for my Arms full of soft, white, kind—Woman! such as I fancy Angelica.
What does Belville mean when he says "not of a quality to give thee any hopes"? On this website called LitCharts, it says that it means Belville thinks the gypsy is too "highborn" to sleep with him out of wedlock. But why would a gypsy be highborn? Could the line mean that the gypsy seems inconstant/promiscuous, so it would not be a good idea for Willmore to fall in love (real love, not Willmore love) with her?
You can read the earlier interaction between Hellena and Willmore starting here.