Red Mandrake - I usually just go to Cyclops Lane and change servers after I clear the area where all of the wizards are standing (in the park). Also check the area by Eyus' Tower, and the two areas near Achilles' Tower.
Sandstone - Stonetown in Zafaria, the first part of it, not the area near Belloq. Just do a loop around, and change servers, and go back the other direction. You can also find it in the Savannah but I've had more luck in Stonetown.
