For selling product online there are many ways but I would recommend that you start with Amazon which is will be great.
You can be vendor and sell products.. Identity your niche and existing sellers thier products and prices accordingly you can make your product listing on amazon.
incase If you don’t want to be a vendor for amazon then you can be an affiliate marketer and make commission on every sales from your affiliate account.
To make affiliate marketing more effect you can use below steps and social media for quikly sales.
Also you can make a Youtube video and talk about product on following aspect:
Once you are done with it upload video on youtube and other social media sites and put amazon link below so that people can buy from there.
If you have good product and price, you need a initial push for that you can use facebook boost with 1000/- budget. Facebook boost will get you good traffic as we as visibility of your product.
Result is totally depends on product quality, price, user experience and marketing.
Conclusion: No matter if you use free tools or paid tools to reach out your target audience, always digital marketing has an important roles to increase sales of any product.