Hello, Shylin! I also use Pinterest to promote visual products and have been able to take an account from 62 monthly impression to nearly 75k monthly organic impression in less than 30 days. ^_^

So for Pinterest, yes, I agree, and I see it myself, content is King. You need to post pins that people like. However, sometimes our pins are new and not yet proven for platform-content fit. Here is where our strategy plays.

If you want to sell, you need to drive outbond click. However, to draw outbond click, you need to maximize impression. So impression is the first metric that you need to keep your eyes on and group board is one of the most effective way to maximize impression.

Here is my strategy:
1. Create your main account, post your main pins on this account. (You already have)
2. Create 3 - 5 more sharing accounts. You need to run those accounts on different browsers. Running them on VPN or anti detect browsers is even better. These sharing accounts needs to have some pins so Pinterest won't shut them down. You will use these sharing accounts to repin pins from your main account to group boards.
3. Join group boards with your sharing accounts (NOT your main account). You can use tools like Pingroupie to quickly find Pinterest groups that are accepting collaborators.
4. Repin pins from your main account to group boards via your sharing accounts. Usually group boards will allow 4 pins only per day, otherwise they will strike the account out for spamming. That's why you need quite a lot of sharing accounts, to maximize reach.
5. Check the analytics, repin pins that get most impression to more group boards.
6. Do it consistently. You will start to see outbond clicks.
7. If you don't see outbond clicks yet, keep publishing even more new pins on your main account, don't stop, you will soon see outbond click.

Here are some good points that I learn from sourcing organic traffic from Pinterest

1. Pinterest loves and will send traffic (impression) to large established board. The number of pins in your account matters.
2. The number of repins matters. It serves as social proof. Pinterest will send traffic or impression to accounts with proven social proof. (That's why we use sharing accounts to maximize our number of repins).

Let me know how your account grows!