Upgrade to an SSD before more RAM.

SSD first, every time. Swapping your boot drive from an HDD to an SSD is the single biggest performance improvement you can make to an old computer. Boot times go from minutes to seconds, apps open instantly, and the whole system feels snappy.

More RAM helps only if you’re actually running out. If you’re not maxing out your current RAM (check Task Manager or Activity Monitor), adding more does nothing. An SSD helps whether you have 4GB or 16GB of RAM — it speeds up everything that touches the disk, which is almost everything.

If you have to choose, get the SSD. You’ll notice it every day. RAM can wait until you see your system struggling with too many tabs open.