Depends on how serious you are about this, gold spray paint may suffice...... or, at the other end, you may just want to buy a gilded leaf. The American Museum of Natural History used to sell some very nice pendants, presumably made via the electroforming process, at reasonable prices; I'm sure they're available from many other sources. (Websearching "gold leaf pendant" finds some 24K examples around $25, and even finds a wholesale supplier.)
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There are 2 ways to do this that I know - 1. Dry the leaf or it will proceed to rot inside the gold layer. - use a desiccant such as Silica gel or put in a warm place for a week or two.2. Thinly coat the leaf with thin PVA (white) glue and cover with gold leaf - there are many places that explain the process of applying gold leaf.OR1. Dry the leaf again, Coat with thin PVA and dip in graphite powder (see a lock smith for some) - This makes the leaf conductive and you can then electro plate it in the normal way - There are web sites covering this process.
Ah just an aside - The chemicals used for gold plating are highly toxic as well as very expensive.If you use the graphite coat method you may need to electroplate a thin layer of copper on the leaf before gold plating.
Have you seen this one?https://www.instructables.com/id/Electroforming-an-Iris-Seed-Pod/
Dry the leaf.Soak the leaf in "wood hardener" available from Home Depot. The wood hardener will make the leaf much stronger. A second method would be to apply thin super glue from an RC hobby store, not the hard ware store stuff, all over the leaf and let it cure.Let the wood hardener dry.Apply gold leaf per the usual method.
If I was wanting a golden leaf, I would use a combination of techniques. First, I would use the leaf to make a mold instead of trying to put it on the actual leaf. Then, you could make a leaf out of the mold using a cheaper metal, and electroplate the gold onto this metal leaf. You should end up with a perfect looking golden leaf!