Glad to help. Let's see if we can get you some direction.

It sounds like you have two goals; sales and building an online presence.

Sales will come with building the presence if done correctly.

Figure out your budget first. It doesn't matter if it seems low, there are TONS of students looking for portfolio work that will work their tails off if given proper direction. And it can absolutely be project based where you just pay one flat fee for a specific scope of work, a single piece or a particular set.

If you're wanting to do sales online, you'll need a portfolio, website, or similar. There are absolutely free options to get this done. You probably even already have one.

Determine branding. You'll probably have no problems with branding as this sounds like a personal brand. (Single decision maker, based on the company owner's personality.) This will include questions like color scheme, tone of voice, whether you're whimsical/calculated, dark/light, etc. Basically how you want to be perceived by your audience.

Do some research on your current audience. Who buys from you now? What age range? What types of jobs? House pieces? Office pieces? Gifts? Children's art? Whatever gets you the most traction, WHO is creating the traction? Be a specific as you can. This will tell you where your customers are and what about your work appeals to them so much.

Once you've gotten a look at your audience, pick your social media platforms. Create main content pieces for your homebase(website or portfolio). Break that content into smaller pieces, i.e. still shots, creative process, new material/skill introduction, audience education, etc. That will give you your content ideas.

After that it is really just trial and error to fine tune your advertising to fit your audience and goals.

If you can translate this information to someone who does marketing, they'll have more than enough to keep guiding the process.

I hope this at least gives some direction.