Spell Burst has a single printing (Time Spiral).
Foils popped a few months back, and have bottomed out again around $5. The art is quite foily. These are excellent pick-ups, as they will likely hold $15 in the inevitable spike that awaits in the next few months.
Non-Foils are probably your best bet. Anything around $0.50 is my target. They're going to hit $2 at least, and $5 potentially, within the coming year. These are scarce, overall. Vendors will eventually be buy-listing these well over $1 apiece.
Buyback seems to be making a comeback. Keep your eye on Memory Crystal, too.