Your best bet is to narrow down your niche to something specific but still popular, like "preschool children with ADHD." That's just an example. Spend some time on keyword planner to figure out which keywords/topics parents are searching for. Compare your keywords with the top search results to see how hard it will be to rank your site for those keywords.
Before you narrow down your search too much, look on some of the major affiliate networks or Amzn to find products you can push. You need either a few high priced products or a bunch of cheaper ones.
Finally, set up your site in an optimized but not spammy-looking way. Write 10-20 good articles on how your affiliate products can help children with whatever health issue you picked. Include affiliate links. Use your keywords and synonyms of your keywords in your articles.
As you post your articles spaced 1-2 days apart, start marketing your site. Set up Adsense. Buy ads, buy followers, comment on blogs, beg for links, etc. Or do more blackhat stuff, it's your dime. But be prudent. Don't send a huge bunch of links to your brand new site. You can also find good brokers to help you buy old domains that already have backlinks and authority.
Repeat. Repeat. Repeat.
After a few months, you should be making money.
