okay, so I will try to help you best I can. I was wood league 1 when I did this PvP quest, and I beat consecutively 7, 7, and an 8, which then I just chalked it up to players who aren't experienced in card games (I been playing card games for many MANY years), i mean some of the things I see amazes me. Also, green shadow is on par if not stronger than super brains, from the perspective of veteran CCG player (if you must know, I played at least 50 different CCG

Few helpful tips first:

1. NEVER drop your 1 for 1/1, any smart zombie players will just leave this alive and not kill it until you buff it, so its basically useless.

2. Almost ALL of green shadow's 1 for 1/1 are bad, the pea shooters are good because you can torchwood.

3. Don't waste her signature power to deal 5 dmg, save it for late game and kill a big gargantuan for 1 sun (bwahaha, love it), her signature power is actually super powerful, and borderline rigged.

Here is the basic structure of a deck I used (don't remember exact, but def F2P)

4x pea shooter

4x torchwood

4x snow peas (or however many you have at this point, if not i would craft them)

4x combo of cabbage and skyshooter (preferrable sky shooter)

4x cattail

4x flourish (in this kind of game, flourish is actually very important to have)

2x podfather (DO NOT get any more than 2, this is one of the slowest cards in the game, I mean ,zombies get 1 for 2/2 that can grow, this is a 3 for 2/2)

3x threepeater

1x the free snapdragon (this card is a good AOE to stop zombie's good early game)

4x grow shroom

3x fertilizer

3x smoosh-shroom

Early Game

Try to defend vs the fast zombies, because mega grow (as a class) is generally a slooowwww class that has much better late game. Do not be discouraged because your early game is not good, because that's just the class, and smarty doesn't help in the early game department either (haha, 2 late game classes). Do NOT kill all the zombies, let a 1 or 2 attack zombie have free swing at you, because green shadow's super powers are sick, so you want to collect those early as possible.

MID to LATE GAME

This is simple, one word, THREE PEATER. LOL, I mean, LOL, how is this common, this is in CCG terms, called a POWER CARD. I mean i get it, it takes a bit of set up, but guess what, the power is craaaaaazy. This card's total dmg is all 3 lane combined. I always save at least a torchwood for this to use on turn 6. Let's make a hearthstone analogy (since that's the popular CCG right now), I think threepeater is on par of the Force of Nature + savage roar combo, if the zombie player doesn't have something that can deal with the threepeater right away, he might as well just concede.