Looks as if you have pinned it very well. My suggestion for the first seams, considering your block placement, would be to make a sort of tic-tac-toe grid. Vertically, if you went right down the middle you would be stitching in the dead center of your blocks. I would stitch down the right and left sides of the middle blocks and do the same for your horizontal lines. Then quilt each block, removing the pins and leaving you about 4-5 inches of sewing room at a time. Some may disagree with what I say next, but it works for me. I quilt the borders down last all the way around instead of going into the borders when I'm making my initial stabilizing quilting lines. You have a lovely quilt and I'm sure you will do very well!