For graphite drawings with a moderate degree of realism, a drawing paper like Strathmore Series 400 will give good results without breaking the bank. It's an off-white though, so won't give the snappy highlights you need for very crisp realism. For tonal drawing, especially with lots of darks, it's worth paying the extra for some Stonehenge paper. While its soft surface doesn't take to lots of reworking, the fine velvety tooth holds the medium well.
Many professional artists opt for bristol board, rather than paper, for their realist tonal drawings. The surfaces are strong, tough and very smooth. A plate finish is good for very fine detail and precise lines, while a velours surface will allow richer darks, but can have some visible texture. It's a good idea to try both to see which suits your drawing style. You can't go wrong with a plate finish Strathmore Series 500 Bristol Board.
Another popular option with realist artists is hot-pressed watercolor paper. Some have too much size and are slippery, but a minimally sized watercolor paper will have an excellent tooth and smooth surface, without the slipperiness of Bristol Plate. This is my personal preference too. Try Fabriano Artistico Bright White or Arches Bright White hot press.
