I would definitely recommend ISO 27001 or SOC2 which is the equivalent in the US, but with a few caveats. Having gone through the process myself I can without a doubt say it elevates your security posture by introducing an almost uncomfortable amount of rigor in your processes and procedures. The caveat here is that it is an intense process - weeks or months to prepare for and the security procedures you put in place are especially heavy for a smaller company. Maintaining these certifications takes a lot of work too and you would almost need to hire a security officer to keep up with it.