Paper

In most cases Printing or Cartridge Paper is sufficient, but sometimes artists prefer to use the real deal and buy materials from shops.

I do most of my drafting with a HB 0.5 pacer, the lead is easily replaced and the lines come out even and smooth. Sketching, I prefer to use a soft pencil sharped with a knife rather than a sharpener. Having waterproof pens is very important, and we'll come to that later. These come in felt tip varieties which are really rather fragile. As for artist's pens, try to have at least 4 nibs.

Normal black ink will do for most of your jobs, but make sure not to use cheap stuff, it'll yellow and fade at the edges and the black wouldn't be as vibrant on the story pages. There are colored ink to be used for cover pages too, but I don't tend to use them due to my art style and my preference for the PC.

Holkein is a good brand that produces watercolors in a tube set. Dr PH. Martin is a good name for transparent watercolors in a bottle form. Both are used often by Japanese manga artists.

Rowney works well, it is smooth and the consistency is pleasant. Try to steal clear of dry, chalky and hard versions, they tend for bad results with manga covers. This medium is also a good match up for watercolor.

Copic Pens are a manga artist's favourite, they allow a range of colors and thickness and are usually vibrant to boot. A little expensive though.

You really need a good durable ruler, try for one with a metal edge so it doesn't wear out too quickly. Compasses are rarely used since they damage the paper, there are rulers with curves and circles in them. Be warned, they are not cheap.

Last but not least, the letratone portion. People often don't realize the shadows and effects on a manga are usually created by a sheet of contact like material stuck to the page, it is pre-printed with dots or patterns to suit the user's needs. There are specialty prints for manga artists.