Greetings, Dupin!!! And welcome to the Misty world!
My first choice would be to take a look to the FAQ on this very site. Along with the book you already have (Which is it? Domains of Dread? The Ravenloft Campaign Setting? The Ravenloft PHB?), it gives a lot of atmospheric information.
It seems you have "Night of the Walking Dead". I've always thought of it as the best Ravenloft adventure (Perhaps because it was my first adventure -as a player), and it works perfectly with low-level characters. Perhaps you may also download the House on Gryphon Hill and the other Hyskosa adventures (Touch of Death, Feast of Goblyns, Ship of Horrors, From the Shadows and Roots of Evil), which are available on the
WotC website, and make a pretty straightforward storyline.
As you explore them, you may take a look on the Gazetteers (I bought them in electronig version at
http://www.drivethrurpg.com, as most books don't make it to Colombia -BTW, I thought I read elsewhere that you're from Argentina? If so, greetings to a fellow Latin-American! -, they indeed contain a lot of information, and for the most part they are useful no matter what edition you're using.
Once you're done (And, trust me, you have weeks, or even months, ahead of you), you may also try to take a look to the Book of S* series in the Kargatane website, and the Quoth the Raven and Undead Sea Scrolls in this site.
With that and your own ideas, you're set for the worse!
(Well, a couple of novels won't hurt, if you manage to put your fingers in one of them)