The Collins top is compatible with a range of different fabrics. Your choice of fabric will govern the silhouette you achieve.
Consider using light to mid-weight fabrics such as linen, linen blends, cotton, gauze, or chambray. For a softer silhouette, consider sateen, silk (crepe de chine or habotai) or viscose (rayon). Be careful if you are a beginner though, as these fabrics are a little trickier to sew. I'd suggest sticking to stable natural fabrics that are not too prone to fraying if you are a beginner.
Softer fabrics will drape over the bust (and create soft flowy sleeves), while stiffer fabrics will create a more voluminous and structured silhouette.
Due to the number of panels in the Collins top, it is a great pattern to use to experiment with color blocking and stripe direction. You can download a free coloring-in template of the pattern if you would like to explore your options before cutting your fabric.