Watch this video and make adjustments accordingly. Some settings eat resources but hardly have any noticeable effect. Main problem causers are view distance and particle density.

It also helps to turn off back-ground processes if you're on Windows 10, follow the instructions here.

Let me know if these changes work for you, Im still playing on an old rig and can get pretty stable 60fps.

Edit: It also helps to add ESO to your anti-virus and firewall exceptions.