When a product reaches a state where my main selling point is useable and obvious i consider it ready as MVP. Marketing is always different. Usually I focus on

When a product reaches a state where my main selling point is useable and obvious i consider it ready as MVP. Marketing is always different. Usually I focus on getting into Google ASAP with some semi strong external Backlinks (your own sites, Reddit in the past, hackernews, etc). To be completely honest here, I pick one or two super relevant subreddits and buy a few (like 10 or 20) upvotes to get it started. It's important to play the SEO game right, so I always have a few 'blog' articles on my sites that talk about solving an specific issue. The following days I search the problem I am solving and plug my site everywhere. Blogs, q&a sites, forums, Reddit comments, no matter how old. Sometimes very subtle without link just the name or so. At this point I usually have a good idea if this product is going anywhere. If it is it's time to focus on building out the MVP according to feedback, otherwise I give it another week or two and see where it's going.