There are only two primary methods of gaining traffic.
1. Organic (free) traffic methods (social media platforms, SEO, etc.); and
2. Paid methods (PPC ads, native ads, email ads, etc.)
If you don't have a budget, then you must focus on free methods and invest your time. If you have a budget, then paid methods will get you traffic much quicker.
For either method, if you don't have the money to invest in hiring a professional to manage traffic generation, you should invest your time in learning SEO.
To grow your blog, essentially you will need:
A) Content; and
B) Traffic