Lovely pattern and kudos for taking on the challenge. Doing a test run with a less expensive fabric to work out any kinks is a good idea. Linen, while lovely, is not the easiest fabric to work with because it can unravel and fray quite a bit while you are handling it during construction. It can also be harder to pick out stitches (almost inevitable if you are teaching yourself as you go along,).
Since you indicated you might like this dress in other fabrics, why not do your "muslin" in a cotton, or cotton-poly blend, broadcloth that you can wear as a casual summer frock? The broadcloth will have a similar drape, but is a much more tightly woven fabric than linen so it is easier to handle--and, if you sew it with a slightly longer stitch length, will be easier to rip out and adjust seams when you need to fix something. You can choose to line this "muslin" frock, just line the bodice, or even forgo the lining altogether.
I'd also prep my fabrics before starting, depending on how you plan to care for the finished garment. Since you'd probably want to wash the summer frock, launder and iron the length of broadcloth before cutting out the pieces. If you intend to dryclean the linen, steam press the fabric length to ensure there won't be any shrinkage when the garment is cleaned and pressed. Same goes for your lining fabric--make sure the cleaning methods for it are compatible with the fashion fabric. And stay away from 100% polyester linings unless you want to feel like you are in a sauna every time you wear the dress. Rayon/viscose blends are more comfortable, and silk is the best! Just remember to wash or steam press the lining fabric as well to avoid shrinkage.
Another tip is to make sure the grain of the linen is straight before putting your pattern pieces on it-- linen often gets twisted when it is rolled up on the bolt by the big machines. Here's how: Straighten the ends of your linen fabric length until you can pull a single thread from selvage to selvage on both cut ends. Fold the fabric in half length ways and check to see if the cut edges line up; if the cut edges don't line up straight (and they probably won't!), you need to straighten the grain until the folded fabric length forms a perfect rectangle instead of a trapezoid shape. Find a helper and get that person to grab one corner of the opened up fabric, you grab the diagonal corner on the other end and start tugging on the fabric. Check every so often to see if the cut edges are lining up straight by refolding the fabric in half lengthwise again.
Prepping your fabric before you cut out your pattern pieces is hugely important if you want a wearable garment, but it often gets ignored in the excitement of doing into a new sewing project. Have fun!