A quick note on the wording first, since it causes confusion: what people call gel balloons are helium balloons. The gel in question is HiFloat, a coating applied inside latex to slow the leak, and it does not change the lifting force. Nothing about these balloons involves gelatine.
Lift comes entirely from the volume of helium displaced, minus what the balloon itself weighs. An 11-inch latex balloon holds around 14 litres and nets roughly 10 to 14 grams of lift, which is enough for a light card or a small tag and nothing more. A 16-inch balloon manages something like 25 to 30 grams, and a 24-inch around 80 to 100 grams. Giant 36-inch balloons carry noticeably more, but they are also heavy in themselves.
Foil is the common misunderstanding. A 40-inch foil number looks enormous but is flat, so it holds relatively little gas and lifts barely more than its own ribbon and weight. Foil balloons cannot carry a gift. If something needs to be lifted, the answer is a cluster of balloons calculated for the weight, and for anything more than a few dozen grams it is more practical to place the item on the ground and let the balloons decorate it.
- Latex 11 inches: roughly 10 to 14 grams of net lift, enough for a card
- Latex 16 inches: around 25 to 30 grams
- Latex 24 inches: around 80 to 100 grams
- Foil numbers and shapes: flat, so they lift little beyond their own ribbon
- To lift a real weight, use a calculated cluster rather than one balloon