Setup a Website related to your niche, create reviews for products in that nice (quadrillion health/bb products available)
Sign up for some Affiliate System of a Fitness/BB Shop, post those links inside your reviews/articles and then share them to your instagram account.
Also apply for adsense, you could generate quite a nice amount of UVs with 200k followers if they are all niche related.
You could also try promoting clickbank products on your website and then share them to your IG account, i think when you post the affiliate link directly your account will get banned.
20$ day should be possible if everythings done right.