O que significa jiggy?

I concur.

It could mean "excitedly/nervously/anxiously", in slangy ways "extravagant" or also "exciting", and so on and on.

A more recent slangy meaning that someone dresses well or looks good (in some kind of clothes).
Getting jiggy with somebody could also that someone kiss or get 'intimate (hook up, and so on) with somebody else, kiss, etc.
Those meaning according to the Urban Dictionary, so it may have local or use privy to some region, group, people, for some time and may be now outdated or may have catched on...

Gostaria de saber o que significa no contexto de elogio para algum interesse romântico, nada muito específico

Difícil em Pry. Pode ser tanta coisa, o contexto irá definir: incomum, esquisito, inapropriado, excêntrico, legal, solto, bem vestido, zoado, fofo, rápido, etc...