Is there a general list of good CEs to keep?

Shinji CEs (aside from Record Holder), Primeval Rune, Lugh Halo, are sh*t.

Self Geass Scroll is garbage, but don't burn (or event MLB), it gives you bonuses for Fate/Zero event rerun, in about 2 years...

Art of Snake is something I would never use, but it gives some bonuses in the Jalter rerun, also 2020, so, keep it.

If you don't wanna max Euryale charm, dont burn Love Potion.

Dragon Meridans is useful for farming if MLB. Same for Sorcery Ore in Casters, a budget Divine Banquet. Rins Pedant is a good Budget crit CE. Moon Cell Automation will give bonuses in a event rerun in the January 2019, plus is okay in split deck 3*s, like 100 Hassan and Kid-Gil.

In general, you don't want to burn ces because they can be used for ce bombs for leveling your more useful ces. Prep everything for ce bombs except Dragon's Meridian. That's the only useful one off the top of my head. Good for F2p farming

3* 50% NP start and Battle of Camlann for Solos. The rest are really bad.

4* Iron-willed Training, imaginary element and divine banquet are good to have. Anything else is fodder.