After going quickly through the Level 1 of SimCity BuildIt, the Level 2 will unlock a new resource at he factories: Wood.
Wood will be required to create the Planks at the Building Supplies Store, but only as of Level 3. Meanwhile the Wood will be used for upgrading buildings.
While at the Building Supplies Store, in the beginning you will be offered to use your SimCash to purchase missing items. You can do it or wait until it gets produced at the Factory.
Quick tip: keep you factory producing non-stop, iron will be required to create Nails.
Level 3 will also unlock 2 more Small Factories, which you should jump on right away. You need to increase production speed and volume. You should place your factories as far as you can from the residential buildings or your SimCity population will start complaining about pollution.
And this is it. Keep producing and upgrading the buildings, you will shortly get to Level 3.