Hi Kris, thanks for reading!
Depending on your product, this strategy works best if you already have a strong social network of friends on Instagram. If not, you can also message big themed accounts (think meme accounts) and find out their shout-out rates.
Another (possibly even better) platform right now is TikTok. A lot of influencers will post about you in exchange for free product.
Either way, the strategy all comes down to which product your niche is in. You'll want to do a lot of research/testing to find out what works best.