Standard Orzhov deck, with some Control and Aggro aspect and Strong monsters like Master of The Feast and Desecration Demon. Almost all Theros block. With the collection rotate, some cards will go out, but can be replaced, like Doom Blade for Hero's Downfall and Desecration Demon for more Master of the Feast.
First remember: Deicide is an AWESOME card, it can easely be on your Main Board, if you think it's better, DO IT. No regrets here, you'll need it almost all the times.
Based on a 3 match games:
-Game 1:
This first match is a field to discover what will you face on the next two matches, and try to see how your oponent play. Start your game calm and try to response your enemy's moves. See what's he playing the deck type and if he's more an aggressive or a passive player. Try to get your Master of The Feast on the table at the turn 3 and Erebos turn 4. He'll probably go for a creature at turn 5. If you can do this and your enemy have no flying creatures, keep a Gods Willing to protect Master or Erebos and you'll need only 4 turns with Master to win the game.
Ok, now you know what's the deal with your enemy. Time to see your side and what you can do to make the deck better agains him.
Mono Black:
If you're facing a Mono Black deck or something like with lot's of black creatures, you might want to trade Doom Blade for Dark Betrayal (obviously!). If it's a only half black deck with lot's of creatures of another color too, you might wanna keep Doom Blade on the Deck with Dark Betrayal. You can take out Ethereal armor. It's a strong aura on a deck with tons of Enchantments, but your enemy will notice that and keep removals to take out buffed creatures. If your enemy have Blood Baron, you might like a Godsend. It can save you. To play here is simple: Keep removing his creatures, try to keep Erebos on table without Devotion and keep taking slowly his life with low creatures that he'll not destroy. Keep strong creatures to the last 10 health point of him.
Aggro Decks:
It would be a problem if you wouldn't have a Sideboard with Oppressive Rays and Drown in Sorrow. Take out some slow creatures like 2 Banisher Priest and 2 Gods Willing. Put 2 Oppressive Rays and 2 Drown In Sorrow. Place your low cost creatures on the table to block, keep removing and stay with some life. Drown in Sorrow is for cases that you have much less creatures than him, like 2x4. Use it to clean his table, don't be bother to lose some creatures too. The turns will pass and certainly his hand too. Your Midgame is much better, if you get there, the game is yours.
White Winnie:
To play here, is something between Mono black and Aggro. You have Glare of Heresy to take out some threats plus doom blade. Your enemy will probably be aggressive on early game, so Oppressive Rays or Drown in Sorrow would be nice to play too.
Midrange Decks:
So nice! it's the easiest one. You're faster then him with nice early threats like Master of the Feast and Desecration Demon and have some nice Removals for the Midrange phase. Just control the actions, keep pressing the Early and remove his Midgame.
Control:
Well, if it's a U or UW control, it'll be a really slow game. The advice here is to get Ajani's Presence to prevent a Board Cleaning from him. Other nice option is to play some low cost cards at the same time. Like Tormented Hero plus Judges Familiar or some 2 drops creatures. Brain Maggot may help you a lot holding some removal, but he can be easily get exiled. Be pacient, wait hes removals get down, keep some for his big end game threats too and good luck!
Green Devotion:
Well, in this case, Lifebane Zombie and thoughtseize would be nice, but we won't have them(LifeBane is M14, will leave standard soon, so i preffered not to invest on it. Thoughtseize is too expensive for me. I'm playing on that reality :D). So, use what you have! Oppressive Rays might be good to keep some creatures with no Value. If he have some Hydras, it'll be better for you, because you can place it off. Agains a Aggro Green, it's more complicated and you'll need some lucky to win it.
Burn Decks:
Aegis of the Gods is your lover here! It will prevents you to loose some important life. Whip of Erebos is your source to get some life. As soon as he loose some spells, you'll get the control of the game. Banisher Priest has no room here, such as Doom blade. Get Aegis of the Gods and Ajani's presence. You're ready now!
I think it's all for now! :D