The recipes I posted mostly call for a light oil - you can use canola which has a very long shelf life or sunflower which should be ok for about 6-9 months. These are the least expensive and easiest to find. The best light oil would be almond, but it does cost a bit more and has a 6 month shelf life. The recipe that uses oil and water - Rainbow Bath Oil - has a shorter shelf life. The bath salts may tend to clump together a bit over time, but other than that should last a long time. I find they last the longest if stored in glass. Be aware that some food colorings may fade over time. If you are unsure, experiment with a small amount first.

Fragrance is such a personal thing, I did not give specific amounts. Start with only a little and add more as needed. You can find small bottles of fragrance oils at most craft stores. Be sure NOT to use potpourri oils as these may not be safe for the skin. For the dry recipes you can even use your favorite perfume.