I use patterned paper and cardstock for each page layout that I do.
I put them in the plastic sleeve protector in the scrapbook.
I don't know about using loose sheets and trying to attach them together. I don't know how that would work.
Some of us use 3 ring 12x12 books and some use post bound scrapbook. Some scrappers use 8x8 or other sizes but we start with scrapbook with plastic sleeves.
I know one person who buys older books from stores and puts pictures and embellies on them and makes what she calls altered books. Those are lovely too!