It depends on you target audience and what they use the most but top social media marketing websites and apps are : Facebook, Youtube , Linkedin , Pinterest.
For any further business marketing and online marketing queries, Feel free to call me.

Try asking yourself - where does my target customer hang out? If your product is targeting professional business people, then LinkedIn would be a good place to start. But if your customers are consumers and predominantly female aged 14 - 25, perhaps TikTok would be better. Older consumers of both sexes are more likely to be on Facebook, so that's also a good place. If you want to sell to elderly consumers, there may be no best place!
Let me know if you'd like to chat further.

Marketing360.com is a solid website with good information. I also found digitalmarketing.org to be an informative website.

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If you're willing to help us with social media, I'll give you a 50 page website template.