IMO the best way to reform is also the most boring.
It's fun to just hop about the board getting random stats, but the most efficient way is as follows
1: do not reform until your exp is capped (9999999 or something)
2: save and reform, try to get 12-18%+ of your highest stat. Rec,SP, etc should only be taken if your rolls do not offer that stat as a possibility.
3: after reforming, spend all your exp on 1 stat, yes your character will be pretty awful with only 50 up, no did, etc. Note that even with 9999999 exp you probably will NOT be able to reach level 500 with it.
4: repeat, be sure that you get 12ish+ for the stat you spent 500 levels on, feel free to pick a new stat between reforms.
This method is quite boring, and makes your characters hard to use in difficult battles. But offers the largest benefits between reforms. Obviously the benefits will start to outweigh the drawbacks after reform #4 or so.
Because of how boring this method is, you may want to do it to only some of your characters.