There isn't much use for a MacBook (13-inch, Early 2008) – other than to
- Run old 32-bit Intel applications that are compatible with Leopard, Snow Leopard, or Lion
- Run old Mac OS X / PowerPC applications, using Rosetta 1, under Leopard or Snow Leopard
- Use its FireWire port to import digital video from an old MiniDV or Digital8 camcorder
- Keep it around for nostalgia reasons, or as an exhibit in a computer history museum
If you were thinking of updating and upgrading it to modern standards, forget it.
That Mac cannot run anything later than Lion. Lion is thirteen major versions behind Sequoia, the current version of macOS. You won't be able to do much Web browsing with it. https security standards have evolved, and browsers compatible with Lion probably won't even be able to connect to modern https sites. Even if you can get to a site, a browser that's compatible with Lion would be so old that it probably would not be able to render the page properly.
Then there's the hardware.
If your Early 2008 MBP has a high-end 2.4 GHz Core 2 Duo, it has Geekbench scores of approximately 171 (single-core) / 307 (multi-core). A 14" MacBook Pro with a low-end plain M4 has scores of roughly 3,813 (single-core) and 14,837 (multi-core).
The SATA hard drive bay has a 1.5 Gbps SATA-1 interface, not a 6.0 Gbps SATA-3 one. If you were thinking that you might drop a SATA SSD in there, I'm not sure how many SATA SSDs would be happy with that.
It is possible to install up to 6 GB of RAM.
Other World Computing – OWC Memory Upgrades For MacBook (Late 2007 - Late 2008 & Early 2009)
But then the question is, given everything else, is it still worth investing money in a 17-year old machine?