As an SEO beginner, should I choose SEMrush or Ahrefs?

I’m just starting to run my own website and I’m still not very familiar with backlinks, keywords, etc. I’ve seen a lot of SEO articles mention tools, and it seems like SEMrush and Ahrefs are the most popular. However, my budget is limited. If I can only choose one tool to help with SEO, which one should I pick? Thanks in advance for your answers!