Maxing Vendors – The main way to get some early outfits is from Sister's
Junk, the main store in Xion. There are some there at baseline, but as you
rank up the shop by spending money there, there will be more available.
When you finish the entire Sister's Junk quest there will be one more
outfit you automatically get.
Tips For Getting New Eve Outfits In 'Stellar Blade'