Consider all of the possible emergencies which can happen. If you do not want to prepare your own kits, there are very good prepackaged kits on the market. You will need to know if the kit you are purchasing has perishables such as aspirin in it so that they can be replaced when they expire. If you decide to prepare your own kits, you will find that many supplies will come packaged in larger quantities than you find in a single prepared kit. Divide the packages into the different kits you are making.
Many supplies are appropriate for all kits.
First aid kits should be kept in containers that are labeled as such. Small containers which can be used for first aid kits can be found as cosmetic boxes, sewing boxes, tackle boxes, tool boxes, etc. If you purchase your supplies first, you will have a better idea what size box you will need to find to store them. Keep the box in a single location in your house, car and work place. Everyone should know where it is.