This is more for the OP but here's a great article on using the Prismacolor markers and the ruler in the picture above.
To answer the question: Behance Circa Dot Grid Paper (it handles markers very well) and an Alvin 0.5mm mechanical pencil. If I'm doing a lot of sketching I'll pull in the quilt ruler and Prismacolor markers.
This is more for the OP but here's a great article on using the Prismacolor markers and the ruler in the picture above.
To answer the question: Behance Circa Dot Grid Paper (it handles markers very well) and an Alvin 0.5mm mechanical pencil. If I'm doing a lot of sketching I'll pull in the quilt ruler and Prismacolor markers.