The link at the bottom gives several methods that should be considered.

Swan Island says...
"Winter Storage--Use a storage medium such as slightly dampened Peat Moss, Sand, or Pet bedding material (sawdust/shavings). Tubers should be stored in crates or cardboard boxes. We recommend lining the containers with 10-12 sheets of newspaper. Start with your packing medium in the bottom and layer tubers and medium until the container is full. Never store in sealed plastic bags or plastic containers. Store in a cool, dry area (temp. of 40-50 degrees). Too warm they will wrinkle/shrivel and too cold they will freeze/rot. Please check your tubers once a month throughout the winter months."

Dahlia Barn says...
"There are many different ways to store your dahlias. We’ll give you a few different methods. Choose the method that you think would be right for you. If one method doesn’t work, try different ways of storing from year to year and stick with what works best for you. You can be as fussy or carefree as you need to be with your dahlias.
The most important tips are:
Make sure they never freeze wherever they are stored.
Make sure they are dry before they go into storage.
Some people will use a peat moss method below for colder climates. Other options are:
Store in clump form or divided loose in paper or plastic bags. No peat moss.
Cardboard boxes, wood boxes, plastic boxes or coolers lined with newspaper.
Keep the temperature at 40-50 degrees at all times during winter storage. The humidity should be kept medium-high to keep tubers from drying and shriveling. Check your tubers at least once a month during winter storage. If they do show signs of shriveling, give them a spray of water from an ordinary spray bottle.
Winter Dahlia Storage / Colder Climates

You can follow the directions for Easy Winter Dahlia Storage / Warmer Climates if you have an attached heated garage or cellar. You can store anywhere that the temperature will stay 40-50 degrees and never freezes. Outside sheds in colder climates will freeze and are not recommended as a place to store your dahlia tubers.
Start with a cardboard, wood or plastic box lined with newspaper.

Our eastern Washington Dahlia Barn.

Add a layer of peat moss for added protection from cold temperatures.
Add your dahlia tubers in clump form or divided.
Add another layer of peat moss.
Add another layer of dahlia tubers.
Repeat the process until your box is filled. You may need more than 1 box if you have a large amount of tubers."

But you can get a big bag of pine or cedar shavings at The big "WM" for $8 in the pet section labeled at bedding. Or a big hardware store should have vermiculite for sale... Just make sure it's not fine- the bigger chunks the better, or it will hold in the moisture too.

I just humbly suggest not storing everything the same way until you have good results for a couple seasons with one method.

I tried the plastic wrap method last year with mixed results. I had some rot and I stored a lot of tubers without eyes because the eyes are not very visible in the fall and you have to divide in the fall if you are using the plastic wrap method. It definitely cut down on storage space and weight though.