Dragons of Tarkir saw a lower print run than both Khans and Fate Reforged. It's also (presumably) the last-ever 3rd set in a block (as Wizards is switching over to 2-set blocks starting with the imminent Battle for Zendikar block). This means that supply is (relatively) low. Don't let this sell you, but it is a consideration that can be applied time and again (for precedent, see the scry lands from Journey into Nyx, as compared to their Theros/Born of the Gods counterparts)
Dragon whisperer showed some promise back at its first showing after release. Burn decks ususally fare well as blocks rotate, due to their speed and simplicity (fewer options upon rotation). This has all the makings of a sleeper. It looks better and better the more you look at it. Mid-game, after burning them for a few turns (as you do in burn), you can get crucial 3 or 4 damage over their heads each turn, with what seems on the surface to be a timmy-bear. And late game, the dragon-creation can be a very big deal when you run out of steam (as you do in burn).
The dragon-creation ability is not breakable, at least not in standard, but in Modern? I think this could see some Training Grounds synergy. A single training grounds makes Dragon Whisperer quite good. Two training grounds makes it a game-ender.
Lots of potential, just about out-of-print, has lots of time left in Standard (Dragons of Tarkir rotates out with Origins, not Khans). I think anything under $3.00 is a good pick-up for a short-mid hold.
Foils are less enticing to me for this card. No reprint is likely while it's in Standard (and again, that's the time window I'm recommending for this card). Therefore, a foil gains you no reprint protection. The foils are already ~ 2x-3x the price of the non-foils, so there's not much room for proportional gains there. Foils are harder to move, and fewer Standard players care to acquire them, as Standardites are quite familiar with the need to turn over their collection as it rotates out of Standard (to buy the new Standard stuff). As a general rule, steer clear of foils for Standard-only specs unless they also hold eternal appeal or if the current foil:non-foil ratio is very low.
The price graph below shows the minimum price in green, median in blue. The breakaway from flat plateau-like price increments in the last week is indicitive of movement, and the context makes it clear that the movement is up. Don't be surprised if there are $6-$8 apiece by Springtime. Definitely a Standard spec, though. Don't get caught with more than you want for play purposes once Dragons of Tarkir does rotate out of Standard.