Very nice in theory, but in practice I have doubts. Nonetheless I really like the concept. I thought of using Pidgeot SW with either holon wp or unown g + drakes stadium to make it do well against Gallade but oddly enough even though I thought of holon wp, Pidgeot d didn't occur to me. I also thought of Togekiss/Gyarados with the same W/p idea then using cesstation crystal after I got the energy I needed to shut down everything else then retreating when I got another Togekiss if I needed more energy, didn't actually build that, just a random idea floating in my head.
In terms of starters you've really only got Sentret. The rest aren't too good, especially Magikarp, since base set I've had terrible experience with using this fish (but I've liked almost every Gyarados including this one and tried fancy combos with them, from base, to misty's, to shining gyarados, gyarados ex... gyarados d). I thought you could use delta basic/pidgeotto instead and play holon lake to make it so all your basics except Sentret can search out stuff like Pidgeotto d, Pidgeot d and Magikarp d, but trainers are pretty limited here and you've already got lake boundary and beach. Furret is very overworked, I think, the deck could work really well if you find a way to relieve the stress the deck places on it.
I also doubt it beats a well played Gallade more than 50% of the time. Okay your plan in theory is to use Pidgeot and force the set up pokemon out so they can't use Garde lvl x and snipe with Octillery if they bring random set up pokemon up. Gallade needs to flip one prize to OHKO Octillery (two with dre) with no way to recover it, you are back to square one, they still have the bring down option. You've only got one in the deck as well which gives you consistency issues of doom. Gardevoir itself also doesn't perform badly as an attacker against you being assured a 2hko on anything you have.
Magmortar I like your chances against. Their best play is sniping Pidgeot d and attempting to get the deck running again, they might get a bit of good set up before you get Pidgeot d but unlike G&G there are far fewer big options for them.
Although most of my comments appear negative I am actually pretty impressed, but consistency, luck screws (they plague every deck but this one seems even more prone to them) and anyone who dares to play something else are going to give you grief.