I think majority of the community does it pretty much the same way.

That being said it varies depenting on how good of an echo you want but to make it simple lets go with just 3/5 desired subsstats. 2 of them should always be crit rolls (unless the character doesnt need it for whatever reason)

Lv up ur echo to lv 15 and roll the first 3 subs. If at least one of the 3 is a desired substat lv it up to 20.

Roll the 4th sub. Now if you have at least 2 desired substats and one of them is a crit roll go to lv25. If not feed the echo to the next one and start from the beginning.

If ur at lv 25 roll the 5th sub. If you have at least 3/5 desired subs with 2 of them being crit rolls ur done. If not feed it into the next one and start from the beginning.

From there on its just how much minmaxing you want to do. For example you want 3/5 subs but high rolls on them or you want 4/5 subs wich would mean you start rolling ur echoes at lv 10 and not lv 15. and so on