Tools
Tools would be primarily used to either put things together or to take them apart. These could be further classified as hand tools and power tools. Hand tools would include all non-powered tools like hammers and pliers. It would be fine to buy these in the dollar store for emergency purposes. However, for those who would rather have something that would last for years, it would be better not to buy them from the dollar store. Spending more money on tools would surely be worth it because these would always come in handy and were very useful.
Batteries
One of the most common uses of batteries would be for backup power. The ones that could be bought in dollar stores would just run out fast because these were poorly manufactured and did not typically use modern formulations. It might leak as well. It would be better not to take the risk and just to go and purchase with brand names instead.