I used to candy a LOT of ginger - usually 10 to 15 pound batches - with left me with lots of ginger syrup. I would combine that with lime juice and pulp to make Ginger-Lime marmalade and to make sure it gelled, I used Pomona's Universal Pectin because it doesn't need additional sugar to JEL firmly - and I mean FIRM!
I used it decades ago to make jellies from wines - so firm you could turn the jar upside down and nothing came out.
Back then there was a fad for "Sangria Jelly" - what can I say, it was the '60s...
P.S. I bought it in bulk - I think it was originally a pound. Maybe 20 years ago. I still have some in a quart jar and it still works! I made jelly from some orange syrup from my last batch of candied orange peel. There is no expiration date on it.
