Two attempts in the polygon modelling

The first attempt for the shoe.Only used the extude tool to build them all,Then,when I wanted to give the facets a thickness,so I uesd the extude again,but some horrible mistakes appeared when I was almost finished!I could hardly corrected them all!I spent approximately 5hours to correct it,but it didn't work.So I decided to use another way to madke it.

I built the shoe by pieces this time, and then extude , it seems more clearer and easier to build, and almost no mistakes in it, I will finish it and then import it to Zbrush to build more details.