Junk silver whenever it is close to spot price.
1 oz lunars either directly from the Perth Mint on release or a few months after release from the dealers.
Generic bars or "buy-backs" when spot is low.
Coins or bars with interesting new features, like the Stacker rounds (1 of each) the radial lines on the Canadian Maple, The latent images on the Scottsdale reserve rounds etc.
A current year kook and koala to add to the incomplete set of Kooks and Koalas.
Anything being discounted while I am putting in an order for other things.
Things I have chosen not to stack...
Past years' versions of a current series (sure there is a thrill in completing a set of Series 2 lunars but that would mean going back and paying a high premium on the secondary market to get coins I missed) You end up getting 90% of the series for a decent price but massively over paying just to get the last 10%.
This is why I have a few kookaburras, mostly remints because they were a decent price, but nothing of the modern versions. A few of the earlier Kangaroos which I can get for $40 but none of the later ones which cost $80.
None of the hyped coins, I never get around to selling any of them and by the time I do in about 20 years' time, is anybody going to care about the Gods of Olympus coins with the black paint wash?
Things I am not stacking but I really should...
The different sized Lunars, in particular the boring ones. I always get a roll, or at least a half roll, of the 1oz size because they are 'limited', the other sizes might not be limited but there are less of them and the resale premiums seem to be much higher than the 1oz. Plus most people can put together a set of the 1oz and there are plenty of other sellers of the 1oz size. But after people have put together a set of the 1oz they turn to the different sizes and realise that these are harder to find, less on the market and more of a 'prize' when you can complete a set.
This is more so for a boring creature like a mouse because fewer people wanted them at the time but as soon as the Dragon comes out everybody gets excited and wants to start putting together sets from previous years.
Goats are pretty dull animals, I should really be putting together some sets of the various sizes of lunar coins while spot is low.