You just opened, give yourself some time here to get established and develop a customer base.
Go to the Forum search here on Etsy and type in the name of the site you are considering.
Read the threads about that site.
Also, go to whatever site you choose to consider and look at the shops that sell in the same category as your items. See if shops there are actually making sales.
Some sites have a " free" period in which you can sign up and try it out for a short period of time. However, some require your Credit Card information when signing up for the free trial. there have been instances of sites charging credit cards even when the shop owner decides the site is not for them. Kind of like those magazine subscription things where you get a few issues and then cancel, but they still try to bill you
So you may want to just sign up as a buyer first,, visit their Forums and get the "lay of the land" as to policy, bugs, etc.,before giving out billing information.
Some sites have free listings for the first so many products and will permit you to link back to your Etsy shop. An example of this is Zibbet who permits 50 free listing and they will let you link back to your Etsy shop. More than 50 listings, you pay a monthly fee, but also get more features.
I have a shop here on Etsy, my own stand alone, one on Zibbet, and 2 elsewhere, where there are some fundamental service issues.
I have found that if you spread yourself too thin, none of your shops do well.
I am concentrating on the ones that are making sales, are reputable sites, have little to no bugs. and will be letting some go as paid up time expires.
When choosing a site, consider the owners, do your own independent research, and what type of site you feel would best represent your
business to the public.
Etsy has millions of members and those members shop here
That is what is called internal traffic, along with the people who find you through internet searches called external traffic..
Many other sites that charge by the month have little to no internal traffic and you must promote your shop , on your own, to internet searches for customers to find you. Much more work and more expensive.
Also, once you get above a flat $10 a month fee for a shop on a selling venue, that only brings in external traffic from internet searches , you may just want to set up your own stand alone through a site that does not control what you sell or your business policies. This seems scary to some, but is quite simple and easy to do.
Many of those start around $12 a month and go up depending on the features you want. You still have to promote your stand alone to internet search traffic, like you would on a selling site that only has external traffic, but you are totally in control and probably will pay about the same. These styes are similar to Intuit, which you have probably heard advertised, but there are many others that are out there.