welcome to another one of my guides.
Goal of the deck is to flood the board with weaker cards and than use Soul of the Forest to gain high value. Also I've mixed in some treants, because they can be played to fill the board and also you'll get cheap 8 attack 8 health Mulchmuncher. Be carefull not to put everything on board, if opponent has clears in deck.
It is possible to upgrade this deck. The best card to add is Wispering Woods, if you can afford crafting it for 800 dust, than go for it. In deck there are a lot of cards, which can fill you hand, so you will get a lot of value from it. Don't forget to play Wispering Woods followed by Soul of the Forest! Another option to upgrade deck is adding Malfurion the Pestilent, the only downside to this card is it's crafting cost. Tending Tauren and Force of Nature are good cards to add too. Also Power of the Wild would fit in to this deck.
Edit: If you meet a lot of agressive matchups you could add Spreading Plague, because it costs 6 mana, you might need to sacrifice some minions to slow down the tempo.
I hope this deck will help you to climb without spending too much, and you will enjoy playing it as much as I've enjoyed creating this guide.
Thank you and good luck :D
Edit: You can also check out my new Special Budget Mech Paladin deck: