The most direct way to increase your FPS is to lower the graphical demand within the GTA V settings menu while running FiveM.

Ensure your RAM is running at its advertised speed by enabling the XMP (Intel) or DOCP (AMD) profile in your computer's BIOS. FiveM is highly sensitive to memory speeds. FiveM Specific Adjustments

Many servers use heavy HTML/CSS overlays for inventory systems and HUDs. You can toggle hardware acceleration for these menus in the FiveM client settings to see which mode offers better stability for your GPU.

Change your Windows power plan to High Performance to ensure your CPU does not throttle its speed to save energy.