Some dirt - the backbone of a good garden

I picked up a pickup load of compost/topsoil blend at a landscaping supplies company in Menifee CA.   It was 25.00 for a cubic yard of the mix and if filled up the bed of my ford ranger.   It would take $150.00 of bagged compost and top soil to fill up my truck if I purchased it at a home improvement store.  It looks like a nice mix but I am going to add some soil that is piled up on site to give it some more texture.  They advised me to add some fertilizer with nitrogen because the mix is still composting.