You have to Consider the following to make a decision:
Monitor Task Manager:
Check your PC's resource usage in Task Manager to identify whether your RAM or storage (SSD/HDD) is frequently maxed out. If RAM usage is consistently high, go for more RAM. If your storage is slow, upgrade to an SSD.
Budget:
Upgrading RAM is often more budget-friendly than buy SSD. However, SSDs offer noticeable performance improvements in terms of boot times, application loading, and file transfers.
Combination:
Depending on your PC's configuration, it might be beneficial to do both upgrades – add more RAM and switch to an SSD – for the best overall performance improvement.