There are many different tablets on the market that work well for graphic design. The regular drawing tablets without screen are the lightest and the least expensive. Prices go up if you opt for a graphics tablet with built-in display.
What matters most for a graphics tablet is pressure-sensitive features and resolution. A good graphics tablet should at least feature 2,048 pressure levels, the higher the better. The resolution should at least be 2540 LPI. If you want to work with the highest possible accuracy and precision, then 5080 LPI are a must.