Choose a niche you can actually stick with
The mistake almost everyone makes is going too broad. A site about everything ranks for nothing and converts no one. Pick a specific corner instead: not fitness, but home strength training for beginners; not software, but tools for freelance designers. A tight niche is easier to rank for, easier to write about with authority, and it attracts readers with clear buying intent.
Balance three things when you choose. First, genuine interest, because you will be writing about this for months before it pays. Second, whether the audience buys things, since some topics have huge traffic but no products worth promoting. Third, whether good programs exist, which you can check against our roundup of affiliate programs in Australia. If a niche has interest, spending and solid programs, you have a real starting point.