One of the best things about reddit was looking for answers or other users with the same problem as you, and since Google didn’t really help with that anymore and instead insisted on giving you business results, the best practice was to put your search terms in followed by ‘reddit’ and you’d find your answer.
If you are looking to return relevant, well ranked results based on freeform queries you’d be better indexing into something like elasticsearch. Otherwise you’ll be reinventing solutions to well understood problems, like stemming as a very basic example.
For the initial release the search is still fairly basic, but A LOT better than the built in search here.
Right now I just look for IF the individual words match ANY of the words in the post title or body and then rank based on the number of upvotes that the post has.
Future versions may look at using elastic search, etc… But for MVP it just looks for the number of hits + the score of the post as I assume the higher the score the more trustworthy the post, and obviously the more matches that to your query the more relevant the post is.