Efficiency is what enough of the player base desires, so naturally, its what drives a lot of content creation, too
I should note that the proper term for a group of squirrels is a "dray" or a "scurry." I like to name my decks in fun ways, but dray and scurry didn't inspire me to latch onto a clever name, so I ended up going with something that plays off of our Squirrel General's name
But keep an eye out for good squirrel cards going late, and you may just end up with some sick grindy green-black decks.
In mint condition, a Charizard from the first set is probably worth about 45-55
With plenty of creatures going to your graveyard, threshold helps Krosan Restorer become a powerful version of ramp
However, make sure you don't have any Active Character on the field when activating Jack's effect