Keroko

It could also be possible that the season 6 finale will see Starlight get a throne of her own and join the mane 6 and the 7th member. However since we haven't see Starlight interact with anyone but Twilight or Spike in any meaningful manner this season, I have my doubts there. So far, Starlight seems more like a side character for Twilight than a character on her own.

I would disagree that you need to understand your talent/passion to get a cutie mark. If we look at Sunburst, he gained his cutie mark by juggling books but did not understand that his passion and talent was in the study of magic rather than the use of magic, and he had a rather terrible time at the magic academy as a result.

Not exactly. Cutie marks appear when you find the thing that 'makes you special', but this does not mean you will understand the thing that makes you special. For example, Sunburst got his cutie mark when he juggled around the books in his living room, but misinterpreted that as a talent for magic itself, while his true talent was in the books about them. Same with Troubleshoes. While he 'found' the thing that made him special, he didn't understand it. But equally important, in neither case did the shape of their cutie mark help in finding out what that talent was. And that's the problem Zephyr Breeze is facing: His cutie mark doesn't clearly represent a talent, a thing that makes him special, and that confuses him since he has no idea what his special talent is. For Fluttershy, she realized what her cutie mark means when she got it, which made the link between her mark and her talent easy. Zephyr hasn't. He has his cutie mark, but much like Sunburst or Troubleshoes, or you and me, we have no idea what kind of special talent it is supposed to represent. That same question we are asking, "what does Zephyr Breeze's cutie mark mean?" is what Zephyr Breeze has been asking himself ever since he got it.

And her lack of realization confused her. She only knew leadership as being loud and trying to take control, but her cutie mark did not come with an understanding of how she should lead. Troubleshoes got a cutie mark that represented his talent as a rodeo clown, but that was never the main thing he loved about rodeos. He loved everything about rodeos, so when a cutie mark appeared when everything went wrong, and the cutie mark resembled a symbol for bad luck, he drew the wrong conclusions. Well, not always. Fluttershy's mark is a trio of butterflies, which represent her quiet personality more than they do her ability to communicate with animals. Sunburst's represents his name quite well, but doesn't really show his talent for magical study. Zephyr Breeze's cutie mark, much like Sunburst's, seems to represent his name. A gentle breeze. Which is also much like his personality, a calm wind that just goes with the flow not really caring what tomorrow brings.

It's not that it negates the need to develop skills, it's that for most ponies their gaining of cutie marks and finding where their talents lie go hand in hand. Twilight gained her cutie mark and at the same time discovered her amazing talent for magic. Yes, she trained hard to get where she was, but how deep her talent could push her was discovered at the same time as her cutie mark. Rainbow Dash always was fast, but the day she gained her cutie mark she realized just how much she loved speed. Applejack was always good with apples, but it wasn't until she realized that's where she belonged that she got her cutie mark. It's easy for ponies who get their cutie mark at the same time they realize where their talents lie or what they enjoy doing. For those few ponies to whom it doesn't, such as Troubleshoes who didn't realize his talent was for rodeo clowning or Diamond Tiara who had no idea how to go about being a leader, getting a cutie mark is a confusing experience. In this case, Zephyr Breeze's cutie mark seems to reflect his personality more than his talents. Not unknown, but certainly not helpful in finding where you belong in the world.

The CMC are a notable exception though. Most ponies don't form clubs dedicated to finding their cutie marks, but just go about their lives and do whatever interests them before stumbling onto their cutie marks and talents.

The second requirement seems to be part of a redemption story that's currently not really going anywhere, which I think is partially due to the authors being stuck on how to handle her redemption. We've already had a 'dragged down by guilt' version with Luna, Discord told the story of a villain resisting redemption -and also did the relapse- and Sunset Shimmer showed us a heroine faced with the consequences of her actions. What is there to tell about Starlight's story that hasn't already been told before?

That I think is the most important difference between Zephyr and many other ponies. Most ponies, when they discover their cutie mark, find it comes paired with a ton of talent in something. Twilight and magic, Fluttershy and animal communication, Applejack and apple farming, and so on. At the moment they gain their cutie-mark, they've generally found their 'place to be.' As a result, most ponies don't go through the 'try really hard on something for a long time before you get good' route that we do. But not Zephyr. Zephyr got his cutie-mark, but no immediate talent jumped out with it. He has to take the long route, and that's a strange place for ponies to be.

He did try things at first though. He just didn't immediately succeed at them, and then gave up when he didn't immediately succeed. After all, what finally makes him succeed is not trying something new, but going back to something he failed at and trying again.

That's the key though, the episode's lesson is "don't worry if at first you don't succeed, just try again." But we never see Zephyr try anything. If we'd seen more Zephyr trying and failing at his jobs before pawing them off to whoever is around, I think his character and the episode's lesson would be more in line. Zephyr strikes me as a character that could have done fine in a CMC episode: He has his cutie mark, but it didn't come with an immediate and obvious talent. So he's kind of stuck trying to figure out what he should do with his life and where his talents are. It's an interesting story that would be much like Diamond Tiara's, but with a twist. However, we'd have to see Zephyr actually trying and failing to do thing before things fall into place.

His absence is most likely just an animation time saver. Every character present somewhere has to be animated, and while they can cheat around with background ponies doing stock animations, Spike -being a dragon and a main character- requires different animations and can't just be dumped in the background that easily. If he's present, he's expected to do something, which means more time is spend on animating an episode because Spike is there. So they just leave him out to save time.

At the very least they're more common. Dragons regularly consume entire hoards of them and they're still around every other corner. Come to think of it, given that Equestria has rock farms, implying that rocks grow organically like plants, it's not such a far-off thought that gems can be grown as well. It would certainly explain why there are so many of them.

Actually the first thing she does in Magical Duel when arriving is antagonize Rarity, so the dislike the moment she arrives is not entirely without reason. But that aside, a noticeable pattern in MLP is that you're generally not forgiven until you say sorry, and after that everything's chocolate chip cookies. So Magic Duel is still pretty consistent. But yes, Starlight's quick forgiveness is something that could serve to be addressed better. Though I'd like to point to this not being unique, after all Discord was forgiven almost immediately even after he had back-stabbed the entirety of Equestria in favour of Tirek and almost destroyed it in doing so. It's really more No Second Prances that falls short here than Starlight, because Trixie did apologize. Kind of. To Twilight. Before running of and making another show to show off, which people didn't like her for in the first place. So in Trixie's case it's less of a problem with Starlight, and more of a problem with the way Trixie is written. But this does bring to mind one thing I do like about the current Starlight: Guilt. Most forgiven villains in MLP don't really step back to think about the days they did things wrong, but Starlight does. To the point where she's having trouble making friends because she's deathly terrified of people finding out what she did.