Surprise the pegasus lives in Cloudsdale. When she hears about a hit new TV show looking for energetic ponies with a bubbling personality and a knack for throwing parties, Surprise knows this role is just meant for her. Celestia, the alicorn princess incharge of the production of My Little Pony; Friendship is Magic, Thinks that Surprise was born to be on the screen as the element of laughter. From her purple balloons to her yellow puffy mane, Surprise is perfect.
But then a pink earth pony comes along. This earth pony is named Pinkie Pie, who has the same ballons and puffy mane as Surprise, and acts just like her. Surprise is surprised to hear that Pinkie has stolen her role.
So Surprise starts a club called "The Almost Popular Ponies", which includes Twilight, Sparkler, Firefly, Posey, and Applespice. But being around ponies with the same problems as her just increases those problems. When Surprise loses it, it's the last mare she'd expect to lift her out of the dumps.
But when Surprise finds out why she didn't get in, her life changes entirely, avoiding the truth, and her relationships with her club changes to as she leads them on a one-way path to a dangerous encounter with Nightmare Moon.
Just a word of advice: You might get a few more readers if you split your description into paragraphs. it's a giant wall of text as is, and can be a bit off putting for that reason.
Ah, are the G1 (?) ponies being trained as back-up Elements of Harmony?
2811666 They aren't being trained as backup elements. But you're right, these are the G1 ponies.
2811701 Not backup, eh? I know! The G1 ponies are the real Elements, but Twi, AJ, RD, FS, Pinkie, and Rares are the backup ones! The Mane 6 were just chosen to do it instead. Or maybe the G1 ponies will be sent to protect Ponyland?
2811780 Close enough. There aren't any backup elements. This element stuff should be explained in the third or fourth chapter.
2812597 3RD OR 4TH? NOOOOOOOOOO!
Awesome take on the G1's being passed up for revised versions of the G3's (at least thier names) and making them the backup elements of harmony (I made the G1's thier distatnt succsessors in "The magnificent Six", but this works too.) Nice making the Equestrian versions so close to the ponies that ripped them off- er. replaced them, REALLY loved how the one G1 who was kept you replaced with Apple Spice, a G3. Very clever and funny story!