I will definitely be joining Gertie's Lady Grey Sew Along. I already have the pattern and have just got together the fabric and the lining as well as the thread, so I am pretty much ready to go.
I chose an inexpensive suit-weight red wool for the shell and a cheap lining fabric for the lining. I have never sewn a coat before, so I thought I should keep the expenses down until I am confident that whatever I sew will be wearable! I also think that my little sewing machine would struggle with a heavier fabric like a wool melton.
I realise that red is a pretty obvious choice, but I don't already own a red coat and it will be nice to have a classic red one.
I haven't bought the interfacing/interlining yet. Reading the pattern, it calls for lightweight fusible interfacing. I suspect that once the sew along gets going, people may suggest different, possibly better options. So I am waiting on the interfacing.