“I'd say for me like the area that I find really hard to nail is the 0 to 50K because 50k months is where you can start having two three channels running in parallel or even I can split the budget between campaigns and start making a bit more of experiments.”

The $0–50K/month budget zone is the hardest in paid UA — most agencies won't touch you until you're through it

Below $50K/month, you can barely run a single channel properly with almost no room for parallel experiments. At $50K you can split across two or three channels, test campaign variants, and start generating enough signal to optimize. This is also the threshold where serious freelancers and agencies start taking you on — making the 0–50K zone both the hardest technically and the loneliest operationally.