Stat Distribution

Apologies if this derails from the R.O.B. training currently at hand, I'll just answer the original question and be on my way...

Although I'm usually more interested in Vanilla training, in which stat distribution is a simple decision, 0/0/0, I do have some tendencies when it comes to training non-vanilla.

I tend to balance offense and defense, speed being the odd stat of the bunch.
Just incase, the regular stat distribution format for ease of communication is
Attack / Defense / Speed

I'm very fond of 60/60/0, it gives very respectable boosts to attack and defense, and keeps recovery at a stable point, which for most amiibo, is usually good enough. When I'm not satisfied with the current speed of the amiibo, I remove from Attack and Defense equally so I can boost speed. For example, 50/50/20. On some occasions, where a character demonstrates a good ability to recover, I can alter the stats to negatively affect speed, so long as Attack and Defense remain even.

I think that although speed can be beneficial, it's actually very situational when compared to other stats like Attack and Defense, which are nearly always relevent, and has provided optimal results when they were relatively equal. If you're planning a stat loadout, speed isn't usually the first thing you're concerned about. An amiibo with usual speed usually will recover, and one with negative speed usually wont. Of course, this won't apply to every character, as Little Mac's recovery is notoriously bad, and Lucario's recovery is rather effective. Each character recovers differently, keep that in mind.

Overall, experimentation is key to finding a loadout you're comfortable with. I prefer 60/60/0 when I'm unsure, but if you take a moment to consider what your amiibo currently can do and what you want it to do, it can be a relatively simple task to think of a loadout you would like.