Hello, I am new to this site and still relatively new to this game, and if you are reading this then hopefully that means you intend to assist me in one of my first deck building conquests.
The purpose of this deck is fairly simple; use your dorks and prophet to ramp out massive hydras with which to swing at your opponent. As for more in depth card choices:
Elvish Mystic and Sylvan Caryatid: this decision is fairly obvious. These are my mana dorks which allow me to get out biomancers, prophets, and hydras/Zegana earlier in the game and put pressure on my opponent
Master Biomancer: puts prophet at 5 toughness making it that much harder to kill via burn, makes mistcutter more cost effective, and makes Kalonian Hydra and Zegana come down that much harder. also has excellent synergy with other copies of himself; 2 assures that everything enters the battlefield with 6 +1/+1 counters.
Mistcutter Hydra: I see people running polukranos as their secondary hydra, but I'm partial to this. Aside from crapping all over blue decks with protection and uncounterability, its X cost is much more efficient than polukranos' even if it's always going to come out a point below the curve; I run ramp, and it has haste, so I'm not particularly worried about something else overpowering it
Kalonian Hydra: the big finisher. it comes out, optimally having been flashed in at the end of the opponent's turn, and then swings away, other than doubling counters it's just a huge beatstick and hopefully win condition. it does feel a little "win moar" so I've been considering running this and mistcutter at a 2:4 ratio as opposed to 4:2 or perhaps even 3:3
Prophet of Kruphix: Rather than accelerating mana in the traditional way, prophet allows me to tap out and not worry about fueling counterspells, as well as allowing me to flash in big creatures during my opponent's end step to create a pseudo-haste condition for my creatures.
Prime Speaker Zegana: She comes down as big as whatever my biggest threat is, and with ramp can act like a midgame draw spell to potentially allow me to grab a combo piece
Bow of Nylea: The swiss army knife of the god weapons. it's mainly here to put counters on biomancer and grant deathtouch should an opponent drop something bigger than a one of my Hydras. lifegain, flying hate, and grave thinning are all just nice extras.
Simic Charm: similarly to the bow, it can serve more that one purpose, but it's mainly here for hexproof to circumvent pesky killspells. the battle trick and single bounce are just bonuses
Cyclonic Rift: clears board for a game winning swing or acts as 2 extra single bounce cards should that be necessary
Dissolve and Plasm Capture: the counterspells of the deck. I prefer Plasm Capture but was worried about the cost and its specificness, so I split it 3:3 with dissolve which comes out cheaper for more generic mana and scrys for added consistency
Note: this is a deck that I intend to build, and only have a handful of pieces to at the moment. I'm not on a terribly low budget with Christmas in a few days, but I can't really afford to buy extra copies of things I don't necessarily need.