Pre-ground spices bought from the shop do not have the same aroma as freshly ground spices. Create the aroma of fresh ground spice by mixing and grinding your own spices. It even gives you the chance to combine and mix spices to meet your taste.
Manual spice grinders are good in that they can be used anywhere -- at home and outdoors. They can be adjusted to mill spices like pepper corns, coriander seeds, cumin, cardamom, mustard seeds etc. Point to note, manual grinders cannot grind big seeds e.g. nutmeg, corn, etc.
A good long lasting manual grinder is made from either stainless steel or iron with no plastic material. Plastic manual grinders are available. However, they do not last long. Find a grinder on Amazon or in kitchen appliance stores. Cost estimate: Sh1, 500 - 5,000 depending type and quality.