Anything wrong?
Well on one level, no - this is a Green deck and it will hit people until they die. You can`t go too far wrong with a straight forward strategy like that.
But on another level it`s quite poor, especially if you are actually trying to be competitive in the tournament. Probably you could answer best if the other people in this T1 tournament are going to be wielding Mox, Lotus, Juzam on the first turn, or are going to be playing the same sort of all-in deck you have here, that would greatly affect your approach to changing the deck. If you expect nastiness then pure speed is unlikely to succeed and you will need to play spoiler cards to break up their defenses - Winter Orb, Titania`s Song, Primal Order, Elven Lyrist etc.
A few general tips:
More creatures, fewer spells - you can win the game with just a Wild Dogs but a Giant Growth will be dead in hand without them. Typically around 30 creatures, mostly very cheap at 1cc, maybe a few good 2cc drops. Overall I would recommend a process of dropping the casting costs of your deck down drastically. It means losing stuff like Overrun but in my experience this sort of deck has dealt 20 damage by the time it is able to effectively make use of Overrun anyway.
The other way to take the deck would mean adding in Gaea`s Really Expensive Cradles in order to get up to 5 mana for Overrun ASAP.
Quirion Ranger (Visions, Common) is astounding in this sort of deck, lets you run far fewer land. In with this them is Land Grant (Masques, Common), if all your land is Forests there is no reason NOT to simply take four of them out for Land Grants. I think there is no reason to run more than 14 Forests as your land, with 4 Land Grant that is effectively 18 and the deck I envisage would run fine from a single Forest.
4 Quirion Ranger (Visions, Common)
4 Llanowar Elf (Basic, Common)
4 Rogue Elephant (Weatherlight, Common)
4 Skyshroud Elite (Stronghold, Uncommon)
4 Skyshroud Ridgeback (Nemesis, Common)
2 Stampede Driver (Nemesis, Uncommon)
4 Spectral Bears (Homelands, Uncommon)
4 Skyshroud Cutter (Nemesis, Common)
4 Rancor (Legacy, Common)
4 Giant Growth (Basic, Common)
4 Briar Shield (Weatherlight, Common)
4 Land Grant (Masques, Common)
14 Forest
Opening hand could easily look like:
Forest, Quirion Ranger, LLanowar Elf, Land Grant, Rogue Elephant, Rancor, Spectral Bears
Which would play:
1) Forest, Llanowar Elf
(Draw Skyshroud Ridgeback)
2) Tap forest, play Quirion Ranger, tap LlElf, activate Quirion`s ability to untap LlElf, play Forest, tap Forest and LlElf, play Rogue Elephant, play Spectral Bears, reveal hand to play Land Grant.
(Draw Briar Shield)
3) Cast Rancor, cast Briar Shield, cast Ridgeback. Attack for 11.
(What you draw is irrelevant)
4) Activate Quirion to untap Spectral Bears, attack for 15.
Speed isn`t everything, but it can be a hell of a lot.
