Give all your strength to caustics. Without it, neither glass nor metal is not interesting.
Alternative algorithms are not stable for you.
Well, we won’t put ALL our strength onto it, since there are many areas that need work. But there is stuff going on with caustics, see Adam’s Keynote from Total Chaos:
Yes, but for now go the extra mile with SPPM or fake it - just shine a light - Caustics Texture
Even later on, skills you gain will come in handy, since faking is always faster than achieving the peak for real 
Give time to the Corona Team. They are working on it and I’m sure that CoronaCaustics will be the best and fast Caustics in the World!
Caustics is a very strong, complex tool to add in a renderer… It’s not like to add LightMix or to create a CoronaTriplanar (^__^)
Look forward to Corona team to give a quick caustic effect in 3.0.
Jarda has also said a few words about the new caustics in this blog post: Chaos: Industry-leading design and visualization software
done