Hey LudwigRocker,
Your right, it's tough being a kid.
Some grownups just don't take kids seriously. Sometimes they just don't remember what it's like to not be treated with the same courtesy and respect that's automatically given to them as an adult. Shame on Mr. Gardener for not remembering that he too was once a 13 year old kid with dreams of being a rock drummer.
So, here's what I'd do if I was in your situation.
1) Research the heck out of three or so electronic kits on the internet. (Sounds like you've already done this step, and have a couple of kits that "fit the bill" both price-wise and have the features that you want/like.)
2) Save up all the money that you need to buy the most expensive e-kit of the three or so that you've narrowed it down to. Keep in mind that you'll have to pay sales tax on the e-kit that you purchase, and you might need some extra items like cables and such. (If the e-kit doesn't come with all the cables that you need already included.) Have your parents help you figure what your local sales tax rate is for your area in Boston, then they can help you figure out how much extra money you need to have to get what you want.
3) Don't buy anything without trying it out at the store first. You definitely shouldn't have to buy an e-kit first, just to have the opportunity to try it out. (Once again, shame on them for not realizing that you are truly interested in buying an e-kit, and not just wasting their "valuable" time.) Mr. Gardener might not let you try any of the kits that you are interested in now, but the day that you are actually ready to buy one, be sure to tell him (or another salesperson) that you are "there to buy today", and that you are absolutely going to try out any of the kits you are interested in before buying anything.
4) So, when the awesome day arrives that you have saved up enough money to get your new e-kit (plus what ever extras you need), you need to make a plan with one (or both) of your parents to come with you to help make your purchase. They don't have to stand right over you if you don't want them to, but they are there to "have your back", so to say. Make sure to actually get to try out all the different e-kits that you are interested in, and ask any and all questions that you have about each kit, no matter how big or small your questions may seem.
You see, even though you were the one who has worked hard to save up the money that you need, your parents (or another trusted adult) needs to be there with you. Having them there helps to ensure that you (as a paying customer) are treated fairly by the staff at Guitar Center, and not ignored as "just another kid hanging out there". It's unfair, it unjust, but like you said "It's tough being a kid".
I hope this helps, and keep on rockin' brother!