How much do GRE score, GPA, and CRV matter when getting into PhD programs for psychology in the US and Germany?
What is CRV?
I can only speak to the U.S. GRE score can keep you out but can’t get you in - so you need to do well, but once you hit a certain threshold it kind of doesn’t matter how much higher you go than that. When I was in graduate school that threshold was probably around ~155 on each section on the GRE.
GPA matters a lot. That’s the best reflection of your academic work that admissions committees have, and undergrad GPA is the best predictor of graduate GPA. Generally speaking PhD programs are going to be looking for a GPA of around 3.5+; anything less than 3.0 is most likely a dealbreaker unless you have an otherwise truly outstanding portfolio.
Other things that matter:
Letters of recommendation. These matter a lot. You should have three from people with PhDs in psychology who can testify to your academic and research skills and prowess. At least one should be someone who has supervised you in independent research - ideally as a research assistant in their lab (summer or academic), but your sponsor for an independent study is a good choice too. These people should all have PhDs; doctoral students are not a good quality choice for letters of recommendation to PhD programs.
Your statement of purpose. This also matters a lot; you will explain to the program your research interests and why you think their program is a good fit (in some detail). Ideally you will get this reviewed by advisors you trust (i.e. other professors in your department) before you send it out with your program.
Your research experience & background. Most competitive applicants to psychology PhD programs have 2+ years of part-time experience as a research assistant in a lab at or nearby their university (i.e., they started doing research no later than their junior year in college, or they picked this up after college). Many (most, I’d wager) also have at least one summer summer research experience as well. The closer your research experience is to your actual area of interest, the better.
If you are interested in clinical psychology, do note that the average goes up a bit - you’ll be competing with applicants who not only have 2-3 years of undergraduate RA experience but also often have 1-3 years of post-graduation research experience, plus some clinical experience like volunteering at a mental health clinic or working with a psychiatrist.
Source: My PhD is in psychology although not clinical.