I'd say for newcomers to the series the best game to jump into is Ocarina of Time.
The game is probably the most accessible to new players and it establishes the most important things about the series' lore. It's also probably the most balanced game of all. There's no element in it that's fishy; as dungeon design, the story, the world and everything else are all good to excellent. Since you have a 3DS, that works out great, get OoT3D.
If you also want to experience what the 2D games are like usually, A Link Between Worlds on 3DS is a good substitute for A Link to the Past, though it builds on story elements from different games. The 3DS also has the two NES and three GameBoy Zelda's on Virtual Console. The very first game on NES may be a good one to start with, snce that was the first game period, but it's extremely difficult and extremely outdated. It's not what Zelda is anymore. I'd especially recommend Link's Awakening because it's brilliant, but since it's a more complicated game I wouldn't suggest it to people unfamiliar with the story and basics of the series.
I wouldn't go buying new systems for a series you've never tried. Buy a WiiU until the new original console Zelda comes out, if you end up liking the series. Wind Waker HD by itself isn't really worth it, if you're not into the series.
Haven't read the whole thread in detail, so I probably am repeated stuff already said, but this is my two cents 
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