Fractional GAEs seem to be the most liquid, but also seem to carry a high premium. Sometimes, foreign GOLD can be bought at or near spot. A few of my favorites: I bought a Prussian 20 Mark, a BU GB Sovereign, and a Mexican Dos Pesos all at spot at a show today. You should gotta be looking for good deals. However, it is best to stick to the widely recognized stuff, unless its for your collection appetite. I'd stay away from the Chinese pandas (too much risk of fakes), and the 1/20 TOZ stuff (too high a premium for GOLD), but Krug, Philharmonic, and well known others are OK.
Bon Appetite everyone; GOLD du jour!!!