Best macOS version

Hi guys , I just got this MacBook Pro running on El Capitan and I want to know which version would work the best on it using open core legacy patcher ,

MacBook Pro (15-inch Early 2008) Processor 2.4 GHz Intel Core 2 Duo Memory 2 GB 667 MHz DDR2 SDRAM Graphics NVIDIA GeForce 8600M GT 256 MB