When I did a scrap quilt I didn't use a border and it looks just right( to me!).It is strange tho because there no right or wrong place to stop adding pieces !!
Like someone else, said I bought charm squares and fabric samples from H of P , but you can end up with colour ranges you don't want.After 30 years of hoarding I reckon theres still enough fabric for one or two more scap quilts .