In a seed stage startup, how many social media platforms would you say is optimal for marketing?

Things to consider: - A seed-stage startup, will probably have little to no budget. - It's very likely that a seed-stage startup is still trying to figure out who their target audience really is. - A seed-stage startup usually doesn't have a product to sell yet, so there still trying to figure out if anyone would even pay/use their product. Willing to hear anything else you have to say?