Custom building a marketplace in ROR with Stripe, but some devs I'm bringing in to fine tune it said that its best to scrap that all and go through magento because it is easier to modify w/extensions. I've never used Magento and the few people I've talked to who have say that it is complicated...
100% agree with Joseph. There are lots of variables here to consider. In addition to how much you've spent, there's the variables of resources for Magento vs ROR that you have, budget that you have, and time that you have.
For instance, we only recommend doing a custom solution (ROR in this case) if you have a large development budget and ample extra budget for changes and revisions, as that's custom development work, which is expensive.
If you have a very tight budget, we recommend Shopify or BigCommerce, spending very little on custom website design and investing in content (great branding, photography and blog posts) and marketing (aggressive social marketing which can be measured and optimized for growth).
Lastly, if you're in the middle on budget, we recommend doing a dedicated installation with an existing solution, such as Magento. We do highly recommend limiting the number of extensions as well, as, again, they can be great but they can also interfere with each other. Magento's technical structure is such that it is somewhat difficult and finnicky to remove plugins, so you need to be very careful with them in the first place. You'll also need to set up a staging server as well.
We've recently completed a bunch of sites on Shopify Basic and Shopify Plus (enterprise), and love Shopify moreso than Magento. We are also in the midst of trying Spree, which I've heard great things on.
Hope that helps!