Unfortunately I haven’t ID’d her white tshirt, easily found in many shops, Margot did wear a pair of LNDR Tempo Compression Performance Leggings. These can be shopped on sites like eBay.
For footwear, she wore Wardrobe NYC X ADIDAS Yung 1 Mesh and Nubuck Trainers, available for £162.
She also carried her trusty Burberry Medium Rucksack in Technical Nylon and Leather in the colour Khaki. Margot also owns this piece in Red and Black. This particular colour is not for sale, but you can buy others of the official website.
Finally, Margot also kept her phone safe with her LeiLoop Crossbody Phonecase Necklace in Green Camuflage which is available for $24.95 for various phone models including iPhone and Samsung.