The speaker promises his beloved lots of pleasure, especially pleasure that has to do with being out in nature. He will show her all these beautiful, pastoral sights and sounds.
Moreover, the speaker promises his lover "beds of Roses / . . . / A cap of flowers, and a kirtle / Embroidered all with leaves of Myrtle." Thus, he promises to take all the beautiful flowers of the spring and make her a bed, a bonnet, and a gown or petticoat. This promise also sounds somewhat sexual in nature; if the lover is lying on a bed of roses, then she is very likely lying on the ground—and we know the shepherd is "passionate."
He also promises her a "gown made of the finest wool" that they will harvest from their little lambs and even lined slippers to help keep the cold out, though they will have gold buckles, too, to be pretty, I suppose. He further promises a belt made of straw and ivy with clasps made of coral and amber. This doesn't sound like a very sturdy belt.
He says, over and over in a refrain, "Then live with me, and be my love." It is unclear whether he is offering her marriage or simply an affair. We know that he feels passionately about her from the title, and he makes lots of promises, but his ultimate intentions are somewhat vague. Because, however, most of the things he offers her will not stand up over time (they are all made from natural things that die or wither or break down), it stands to reason that his feelings will do likewise.