You really should include
Swiftfoot Boots 
and
Hall of the Bandit Lord 
. Boots is especially nice since it makes Avacyn (and by extension, your entire board) VERY difficult to deal with. You also need some more card draw.
Mind's Eye 
,
Illuminated Folio 
,
Staff of Nin 
, and maybe
Mentor of the Meek 
are some of your better options.
In decks like this, I really like to include a bunch of cards that can recur each other. I'll paste something from a guide I wrote that should give you some ideas.
RECURSION ENGINE
What mono white lacks in card draw, it can often make up for with its recursion engine. The idea is to play defense, wipe the board when needed, and over time your dead things will start to become more and more difficult to keep off the board. Here's how the engine fits together. The first card is what is doing the recurring, and the following cards are what it recurs.
Reya Dawnbringer 
/ Artisan of Kozilek 
/ Karmic Guide 
- each other, Sun Titan 
, Reveillark 
, Salvage Scout 
, Sanctum Gargoyle 
, Razor Hippogriff 
, Order of Whiteclay 
, Argivian Archaeologist 
Sun Titan - Angelic Renewal 
, Emeria, the Sky Ruin 
, Eye of Ugin 
, Crucible of Worlds 
, Mimic Vat 
, Sword of Light and Shadow 
, Petrified Field 
, Buried Ruin 
, Haunted Fengraf 
, Salvage Scout , Order of Whiteclay , Argivian Archaeologist
Order of Whiteclay - Salvage Scout , Order of Whiteclay , Argivian Archaeologist
Crucible of Worlds - Petrified Field , Buried Ruin , Haunted Fengraf , Emeria, the Sky Ruin , Eye of Ugin
Petrified Field - Emeria, the Sky Ruin , Eye of Ugin , Buried Ruin , Haunted Fengraf
Buried Ruin / Salvage Scout / Sanctum Gargoyle / Razor Hippogriff / Argivian Archaeologist - Crucible of Worlds , Mimic Vat , Sword of Light and Shadow , Sanctum Gargoyle
Eye of Ugin - Kozilek, Butcher of Truth 
, Ulamog, the Infinite Gyre 
Mimic Vat - Sun Titan , Reveillark , Karmic Guide , Salvage Scout , Sanctum Gargoyle , Razor Hippogriff , Order of Whiteclay , Argivian Archaeologist
Sword of Light and Shadow - Sun Titan , Reveillark , Karmic Guide , Reya Dawnbringer , Artisan of Kozilek , Salvage Scout , Sanctum Gargoyle , Razor Hippogriff , Order of Whiteclay , Argivian Archaeologist
Emeria, the Sky Ruin / Haunted Fengraf / Angelic Renewal - Sun Titan , Reveillark , Karmic Guide , Reya Dawnbringer , Salvage Scout , Sanctum Gargoyle , Razor Hippogriff , Order of Whiteclay , Argivian Archaeologist
Reveillark - Karmic Guide , Salvage Scout , Sanctum Gargoyle , Order of Whiteclay , Argivian Archaeologist
Kozilek, Butcher of Truth / Ulamog, the Infinite Gyre - EVERYTHING...eventually...but more importantly they protect the rest of the engine from graveyard hate.
If it helps, you can draw a web and connect all of these visually. It's pretty impressive. Artisan of Kozilek can be shuffled back in by the other eldrazi and recurred with Eye of Ugin, and if you want more recursion, Pulsemage Advocate 
is strong in some environments.
Here is a list of all of the pieces for convenience:
Petrified Field
Buried Ruin
Haunted Fengraf
Eye of Ugin
Emeria, the Sky Ruin
Salvage Scout
Angelic Renewal
Crucible of Worlds
Mimic Vat
Sword of Light and Shadow
Pulsemage Advocate
Argivian Archaeologist
Order of Whiteclay
Sanctum Gargoyle
Razor Hippogrif 
Karmic Guide
Reveillark
Sun Titan
Artisan of Kozilek
Reya Dawnbringer
Kozilek, Butcher of Truth
Ulamog, the Infinite Gyre
Also, consider an Eye of Ugin and some colorless creatures. It's a great way to win the late-game, and Kozilek, Butcher of Truth and the Eye itself give you good card advantage. Wurmcoil Engine 
's pretty nuts with the recursion engine I gave you.
...And where's your Steelshaper's Gift 
?
