Hi!
I've played mtg for over a year but I haven't been able to make very good decks. My last and the best deck I've made is a white damage preventing deck:

Lands:
1 Nomad Stadium
19 Plains

Creatures:
1 Sanctum Guardian
1 Mine Bearer
1 Icatian Moneychanger
1 Aven Redeemer
1 Hunted Lammasu
2 Wall of Resistance
1 Diving Griffin
2 Devoted Retainer
2 D'Avenant Archer
1 Volunteer Militia
1 Shieldmage Advocate
1 Konda's Hatamoto
1 Harsh Deceiver
2 Vigilant Martyr
1 Icatian Infantry
1 Mothrider Samurai
1 Benevolent Ancestor
1 Mesa Pegasus

Other Spells:
1 Awe Strike
1 Roar of the Kha
1 Circle of Protection: Black
1 Holy Day
2 Indomitable Will
2 Moment of Silence
1 Angelic Blessing
1 Samite Ministration
1 Force Bubble
2 Vigilance
1 Candles' Glow
4 Sandskin
1 Renewed Faith
1 Healing Salve

The deck can be reformed totally as long as the idea stays. I want a good deck mostly against black- and artifact-decks. My budget is less than 100$ or € if we assume that I have only those cards. I don't need a side deck.

So, please make a good deck which I could use until I learn to make my own good decks. I trust you and your skills in building decks. I hope that you fix this deck as soon as possible.

With respect: Bitten(nickname)

Well, Bitten, thank you for your trust in my abilities.  And let me just say how much I enjoy the fact that you've actually put Icatian Moneychanger to use.  This deck is a joy to behold, perhaps because I had to look up most of these cards on Gatherer to see what they do.  The only trouble is, this deck falls into the old trap mindset of "if you can't kill me, I win".  Life gain and damage prevention are all right, but the best defense is a good offense.  A game of Magic is war, my friend, and you'll never win if you have to hide behind damage prevention shields for the first twelve turns.  What happens if your opponent uses a milling deck and grinds away your library, never bothering to deal any damage?  Or if she plays Door to Nothingness?  You can't give her time to set that up.  Let's see if we can't give this deck some teeth.

Now, I notice you've got 2 Vigilance.  Let me tell you, vigilance the ability is great, because a creature can attack and then still be able to block.  But Vigilance the card is pretty bad; it makes the creature it's on more likely to be in combat, thus more likely to die.  And when it does die, you've lost two cards.  Take out Vigilance, and we'll add plenty of creatures that already have vigilance on their own so you won't need them as much.  Better yet, replace them with Serra's Blessing, so all your creatures can have vigilance!

Next, we need to take out all the cards that are too limited to be of use.  By "too limited", I mean the circumstances under which they excel are too rare.  And for this deck, that means all the cards that don't do anything except prevent damage.  That means Samite Ministration, Shieldmage Advocate, Vigilant Martyr, Konda's Hatamoto, Candles' Glow, and probably all the creatures with banding.  As much as I like Icatian Infantry, most players today struggle with the concept of banding, and it's just not worth your time to explain what it does.  Holy Day and Awe strike can stay, simply because Awe Strike acts as a life gain spell while Holy Day can negate an entire combat phase, plus they're both instants so they can surprise your opponent.

Now, to replace those, there are plenty of 2/2's with neat abilities for WW, and any of those would take you far.  Right now the best ones are probably Leonin Skyhunter, Hand of Honor, Veteran Cavalier, or Samurai of the Pale Curtain.  Other creatures you could consider are Courier Hawk, Inner-Chamber Guard, Aven Flock, or Paladin en-Vec.  You said you wanted the deck to be good against black decks, so Hand of Honor and the Paladin are probably your best bets there.
You also said you wanted it to be good against artifacts.  Well, for that try Circle of Protection: Artifacts, Disenchant, or Kataki, War's Wage. 

The last problem is that you have a lot of single copies of cards, a common problem.  But not so much a problem for you, as many of your cards serve similar purposes.  The deck isn't quite as unpredictable as it would otherwise be.  Still, you could definitely use more copies of Roar of the Kha, Volunteer Militia, and probably Mothrider Samurai.

Finally, in a deck so full of small white creatures, Glorious Anthem will help out splendidly.  Hope it works out well for you, Bitten, and thanks for the E-mail!