If you want to do it without investment, keep building it.
Pick a topic and keep adding info about it, the engines will pick you up and move you up, and people will find you.
This doesn’t happen over night, this is real work and it can take a long time to get rolling well.
Once you are rolling, you still need to make it better all the time.
If you have money to buy advertising with, make sure you read CAP before buying. It can be done, but there are many pitfalls.