You do not need to use much crystals. Crystals will usually absorb more then 300% of their dry form..... meaning whatever amount of dry crystal that you decide to use, it can absorb over 300% of that in water volume. A teaspoon will be A LOT of water crystal.
If you are using it just as a water source for crickets, start with a small pinch of the crystal and place that in a bowl, slowly add water until the point that the crystals can no longer absorb any..... at that point it would be referred to as a gel.
Generally you do not want to reuse any remaining(rehydrate) gel for sanitary reason, use start a new batch. Experiment by starting with small amounts and see how long it takes your crickets to consume in a couple of days and go from there. Key is not to create this massive ball of gel, just enough for them to consume in a couple of days (tip-change out the gel at the same time you change out the carrot/leafy green).
Hope this all helps!
These cricket pillows are just about the same thing. Crystals inside a mesh like type bag to keep it neat and organized. Do not recommend reusing the bags, better of using regular crystals. Once saturated, drop it inside the feeder tank, keep the gels on a plastic/deli lids for ease of cleaning.