It depends on what country you live in, what industry you want to test for, what your personality is like, what other experience you might have, what businesses are looking for this year.
For example I personally believe that the ISTQB course material is a hindrance to the understanding of testing; the language is restrictive and the exam seems poorly written and designed so that it does not even test the knowledge the course pretends to teach and the whole thing is a scam to try to paywall entry into testing… but some countries love it, some industries love it, some businesses require it. In that case I think an ISTQB course would be an obvious good career move to get a job.
This brings up the point that not all courses are for the same thing. I think it’s important to find people you respect and take courses by them to inspire you and expand your horizons, and to fill gaps in your knowledge (e.g. taking a course on a specific technology so you can better understand its place in your business’ tech stack). You may have to get a certification to meet some mandated requirement. You may think your CV is a little light on examples and need to add something useful to it. You can fill in a gap in your employment to show you’re keeping up and still interested. Know why you’re going into a course to help inform you which one to choose, if any.
I know that I would rather hire a newbie who is eager to learn, thinks for themselves and takes pride in their role than someone with experience and a list of certifications but relies on artefacts to tell them how to think or believes processes are prescriptive and requirements documents are complete and sufficient. And above everything I’d rather hire someone that gives a shit than someone that doesn’t despite literally everything on their CVs - people don’t do the right thing they do what they want, so you have to hire people who want to do the right thing. I don’t know a course that would prove any of these things, but I’d be happy to see a lot of learning of any kind on a CV backed up with conversation that they care about what they learned there rather than collecting them like pokemon. Not everyone feels this way or thinks like this, and it will depend on who’s potentially hiring you. Perhaps a good start is to reach out to the sorts of companies who you would want to be hired by and ask them if having done a particular course would be important to them.
It also depends on who you are and what you’re like. Your personality, way with with words, examples of your work and self-organisation and propensity to improve, all things that can do in place of courses to help getting hired. Also if you are in a group that is discriminated against. A course is one way (of many) that can be used to help lead people away from assumptions about laziness, unprofessionalism, incompetence and so on that hiring folk can come to just by making assumptions based on your race, sex, height, weight, if you have a beard, and other factors that come out of employment studies.
Also money. A tighter budget means you’re more on the lookout for free opportunities - volunteer work, testing open source projects, self-learning, free courses, webinars, being active in online discussions. Then get the job and have them pay for the courses you want.