Can someone explain to me how different ADD/ADHD Medications work?

Hello - I am new to this forum and am glad to have found it.

I am an adult female with ADD. I was diagnosed as an adult and have tried most of the popular ADD/ADHD medications that have been on the market for the past 10 -12 years. I am currently on generic Ritalin (Methylphenidate) with limited success. My Dr has suggested I consider trying Focalin or Vyvanse. I do not have a prescription plan so I pay for these out of pocket and I understand they are very expensive $150- $200 per month. I currently pay about $60 for generic Ritalin.

I would like to know what peoples experiences have been with the Focalin and Vyvanse. Is it worth the expense? I would like to try Provigil as I have heard good things, but I just got quoted $300 out of pocket, so that one is out.

Thanks in advance for your help.

Added: I would also like to add that my life is basically in shambles at this point. My relationship is on the brink of falling apart, I haven't worked outside the home in over a decade and I am getting desperate. I see a therapist (one more in a string of dozens) with little results. I really need to find out why I am not getting results...what am I doing wrong?