Dude,
He said he is a first time grower!
It is a common mistake to just buy dirt... I personally make my own dirt!!!
60% Potting soil
15% Perlite
10% Worm Castings
10% Building Sand (or any clean sand)
5% Veg State Nutrients (High in Nitrogen)
But what you wanna do for your seedlings is just use the potting soil, after about a week or two you can put them in your good dirt! Another thing you wanna do is after you mix your dirt get it moist, cover your container and let it sit for a couple days. This will bind your mixers into one livable unit.....your new dirt!!!
It doesnt hurt to throw in a little Blood Meal for extra Nitrogen!
Hope that helps!