An online store takes more than just a platform and a product to be successful. Taking a few steps back - the best starting point would be to identify and engage an audience for your online store first. The only way to do that in the e-commerce space is through digital marketing. Build out a plan for targeting your market - find what stores they already are shopping at and see how you can present your product in a way that will attract them.
1) Market research - define an age, gender identity if applicable, income, lifestyle traits, and what value you are bringing to the table for the individual consumer. What problem are you solving?
2) Develop a proper branding approach - logo, colors, fonts, photography style, verbiage style. A consumer who isn't just looking for the cheapest price, is looking for a brand that feels like something they identify with. There are people who love Louis Vuitton and there are people who love Hot Topic. Who is your target? How can you make your marketing plan attract them?
3) Share your vision through IG/Tiktok/Youtube - as an e-commerce store, you need to have an online presence. This gives consumers the chance to get to know the brand, to become a part of your community, and to know about the latest launches you have along the way. Build your community in advanced and they'll be excited to purchase from you in the future.
4) Website - While working on all of the above, you can build your website - there are ups and downs to all websites so it will depend on you as to how much money and time you'd like to spend building the site in the background before your first big launch. Shopify, Squarespace, and Wix are the most common entry-level website platforms for e-commerce. Squarespace being the most user friendly of the three. All are a great starting point, but you're looking at 30-50/month so building the site and paying monthly fees before you have a single sale or audience member is a waste. You'll also pay fees per transaction so be sure to understand proper pricing structure for wholesale, retail, and shipping locations. Once you have enthusiastic audience members for your launch, go for it!
5) Don't forget SEO! Search engine optimization is the way places like Google show your site to potential clients. You have to have proper metadata, image alt text, content, and indexing in order to tell search engines what your site is all about. This will help people organically find your store even if they have not found your social media pages.
6) Remember there is no get-rich-quick...you will have to continue to monitor your social pages, stay fresh with your content, and see what does/does not work for your business. If you are in the US, the Small Business Administration has tools at sba.gov that can help you as you learn to build a proper business from this idea. They also have SCORE offices in various regions to help with business and legal advice. Good luck to you!

There are a lot of different ways to get money for your vision. Start locally, then branch out find more options on the national level. Your local arts council or other non-profits may have opportunities for you to spread your message and gain more traction and attention from likely benefactors.

Holding art and music showcases, selling tickets to the shows, and fundraising, are great ways to get in touch the arts community and find some backers the organic way and all the while you can fill out grant applications. For many grant applications, illustrating the need for the ultimate goal, as well as, your actionable steps that you've done to move towards that goal are very important.

In order to find something specific to you in your area, I'd reach out to your closest SCORE office (put on by the Small Business Administration) who can help you get set up with free business and legal advice to get you started.

Just doing a quick "grants for artists" search comes up with a bunch of options, it would just depend on what you're looking for and where you're located in order to be eligible.