With the sewalong starting next week, I wanted to share all of my recommendations for fabric and notions for the Riley so you have time to source them before it starts. I have made lots of these during the development of the pattern, so I have pretty strong opinions on what does and does not work for the Riley. Let's start with fabric.
The Riley suggests medium to heavy bottomweight fabrics with little to not stretch, such as denim, corduroy, twill and linen. It also suggests you keep the strength of your sewing machine in mind when choosing a fabric. I can't stress this enough. There are multiple places in the pattern where you are sewing thru 4 or 5 layers of fabric. If your machine is not a sturdy, you may want to consider something on the more medium weight side around 5 or 6 oz fabric. If your machine can handle it, I think that fabrics in 8-12 oz range work great as well.
I sewed up all of my model samples in bull denim. All but the white were from Blackbird Fabrics and the white denim was from Fabric.com. All of the fabrics were nonstretch and 100% cotton in the 9-11oz range. You can use fabrics with some spandex in them if you want. It may add a bit of comfort, but it's not necessary with the oversized fit of the design.
Corduroy is another great option for the Rileys. It really adds to the 90s vibe of the pattern. A heavy weight linen or twill is also good for a lighter weight version of the pattern. Just keep in mind that these fabrics are more likely to bag out with wear and so you may want to size down.
Pocket Lining Fabric
You will need to source 1/2 yd of fabric for the pocket lining as well. Most likely you can just use some scrap fabric that you already have. It's a really great way to use up scraps of fun designs. Suggested fabrics include quilting cotton, cotton lawn, cotton voile, linen, and rayon bemberg.
You are also going to need quite a few notions for this pattern. Some can be harder to source than others, so I will give some resources.
Do not forget to buy a heavy duty jeans sewing machine needle for this project. You will definitely break a needle if you don't use one.
You will of course need some coordinating all purpose thread for sewing up the pattern.
You may also want to use some topstitching thread. This could be matching or contrasting for a fun look. Either way, you use the topstitching thread in just the upper part of the machine, not the bobbin. Personally, I like to use Mara 70 as my topstitching thread. It's thicker than your all purpose thread, but not as thick as traditional topstitching thread so it's easier on your machine.
You will need some interfacing to reinforce some areas of the pattern. Choose a medium weight fusible interfacing. I personally prefer a weft interfacing, but anything you can get your hands on should be fine.
Now for the fun part. You are going to want some overalls clasps and sliders (1.5" or 33mm wide), as well as six matching jean tack buttons (17mm or 11/16"). We now carry Overalls Hardware Kits in our shop that work perfectly for this pattern. If you are outside the US, I would check the Foldline, Blackbird Fabrics, Kylie and the Machine and Closet Core Patterns as they all source Overalls kits and jeans tack buttons as well.
There are a few tools that will make sewing and attaching hardware easier. You may be able to find something similar to use that you already have, but I wanted to show you what I use in case it helps.
Awl - This very pointy tool helps you pierce the fabric where your jeans tack buttons will go. It's super handy and I use mine all of the time. You may be able to find something around the house to substitute though - maybe a nail?
Hammer - A general hammer is a must. I always keep one in my sewing tools. You will want a hammer to attach the jean tack buttons securely.
Anvil - A small anvil is a nice tool to have to hammer onto (saves your countertops). I bought mine at a leather store. I have heard you can also use the back of a cast iron pan in needed.
Clapper - This little tool is essentially a piece of wood that you can use to help set permanent creases in fabric during ironing/steaming. I find that it really helps set the seams when there are multiple layers of denim. I assume you could use a scrap piece of untreated wood you have in the garage as well.