Best/most cost-effective ECU reflashing tools

Hi,

I've been watching the videos and studying ECU tuning, and I'd love to put all the stuff I learned into practice and slowly start offering it to interested customers.

I see HP Academy offers WinOLS courses and I love them, the issue I have is there are a lot of other hardware/software solutions on the web and wouldn't like choosing the "wrong one" since it's pretty expensive stuff, so if anyone could give me some help, it would be much apprereciated.

Cheers