Get an argy and anky and go to a place where there is a lot of obsidian nodes and smack away with you anky and then put the obsidian in your argy because of the weight reduction and fly back to base. I have gotten 4 stacks at a time with this method.
An awesome way to get polymer on the mobile version is to set up a bed next to the Skylord cave. Run the cave and use an Argy to get to blue ob. Look for a Revival Platform. Place it. Demolish it. Easy 10 poly, 100 metal ingots, 25 crystal, and about 13 electronics.
A few ways I know of getting a bunch of this include going to drops that are yellow or above and taking the stuff made at a fabricator and grind it or you can take an anky mine some obsidian rocks and take a megatherium to a cave with a bunch of bugs and than use a doedicurus to get a bunch of stone or you could kill a bunch of titanyroma drones and soldiers with a frog