For pokemon investing - the best strategy can be summed up in one sentence - Target popular items going out of print.
These 2 attached products fit the bill very well, with CZ positioned better because it’s older. If you think these are expensive now, wait and see their price in 5 years.
PC etbs experience this faster than other products, see Prismatic pc etb, because of limited print run.
All sword and shield booster boxes to 1k within a year, 2 max