I've done everything carefully but I never have enough DNA points to evolve. What do I do?

A strategy that has worked for me on every mode there is is to basically just evolve infectivity (like blood, water air, etc.) and NEVER get any symptoms. The moment you do, they will find the cure really soon. When you have the whole world infected and a good amount of DNA saved up you'll want to get 'total organ failure' and gangrene. Or really whatever you have enough DNA to spend on. Another helpful tip would be to get immunity to antibiotics, and maybe if you're feeling rich get the climate upgrades. If your disease ever evolves any symptoms, always devolve them. When the whole world is infected, get rid of transmissions to save DNA.