If you are sewing up the Merritt, you are going to want to source a few notions, as well as possibly some tools that make sewing up a button-up easier. Here is a list of the things you will need (and might just want) as you make your own.
Notions
Interfacing
The first thing that you are going to want to source is some light to medium weight fusible interfacing. I like to use woven wweft interfacing, which I buy from Mood fabrics or Blackbird fabrics.
Or I also love using tricot interfacing which is technically a knit interfacing, but it's really nice and soft so works great for less structured fabrics for a very soft interfacing affect. I usually get mine from Wawak or Blackbird fabrics.
One interfacing item that I absolutely love, but is not required, is 1 inch fusible by the roll which I get from Wawak. The front button placket is 1" wide so this roll makes it super easy to apply.
Thread
You will of course need matching thread for your project. I always buy matching thread from the fabric store I get my fabric from if they offer it, but if not I buy it from Wawak. Gutermann Mara 100 is my go to.
Buttons
You will need quite a few buttons for your Merritt. You can source anything between about 3/8" and 1/2" depending on your preference. My go to buttons are the size 18L Flat Edge Shirt Buttons that come in a pack of 144 from Wawak. I also have their colorful shirt button pack in case I want to be a bit more fun, buy honestly, I usually prefer the basic cream or white ones.
Tools
Buttonhole Foot
My guess is that you already have one that came with your machine, but you are going to want a good buttonhole foot. There are a lot of buttons and buttonholes on this patterns so it is worth having a great buttonhole foot and practicing it before using it on your finished Merritt.
Button Hole Opener
You are going to want an easy way to open up those buttonholes once you have sewn them, and my preferred way is with a buttonhole opener kit. It comes with a buttonhole cutter knife, circular punch, and a hardwood block. You will also need a small hammer. If you don't have one of these you can also use a pair of very sharp scissors, but believe me when I say this is worth it.
Sewing Gauge
This is another one of those "nice to have" tools which I don't regret buying at all. The Merritt does come with a buttonhole placement guide, but if you decide to place your own buttons, this is really handy. Essentially it expands and helps you place your buttons evenly along the button placket.
Marking Tools
Make sure you have some good, precise, marking tools to transfer things like pocket markings and sleeve placket markings. I use the ultra washable crayola markers in a similar color. I know that is not super professional so just use whatever you prefer.
Glue Stick
This is another one of those things that is very optional, but one of my favorite nonprofessional sewing tools. It is great for colors, sleeve plackets and cuffs, and collars. Its much more precise than the bulk left after pinning. I just use elmers, but I do know that there is a sewing version that they sell too. Just always be sure to let the glue dry completely before sewing so that you don't gum up your machine.
Pressing Tools
It is really handy to have a tailors ham and other pressing tools like a clapper to press the curved and hard to reach areas on your Merritt. If you don't have a tailors ham, be sure to get a towel and roll it up to use on areas like the sleeves and neckline. It makes a big difference.
OK, I think that is it. We have a full sewalong starting in about a week which hopefully gives you enough time to gather the supplies and fabric needed to sew along with us. If you still need to get the Merritt pattern you can grab it here.