Str - Def - Health - Speed What cap do you guys have for training each one? Like I know someone said 6k was enough for speed and 13k was good for strength. Anyone agree/disagree?

It's up to you, there's no global truth on the matter. Picking a build because someone says so is never as good a decision as knowing what you want based on how you play

I suspect no matter what build you end up with, it'll be enough to kick the butt of any challenger past and present, very easily, as it is the case for me.

This is gonna sound like an 'easy' advice but make sure you know what each stat does. Many battlers, even up to tier 13 don't actually know, which usually leads to their own confusion when it comes to deciding how to distribute stats.

If you know the actuals formulas, you can decide whether that extra 1K strength or defense is worth it over say, health. If you know what speed is for and how likely you are to critical hit an opponent based on their own speed, then you can figure if it's worth getting any. Eventually, even if you're favoring a stat or two over the others, 35K is a lot of stats, way more than what is needed, so it's good to be able to benefit fully from every aspect of battling, not just sheer attack or overheal.

As stated, the stat max of 35k is a lot of stats you have to play around with and decide what you want to gain. Some weapons work best if you have, say 5k speed. Other weapons may work best if your strength >def or if def > strength or if strength = def. It all depends on your battling style and what weapons you have. I personally plan to have at least 4 battle pets with 4 different builds. For one pet, I know I want to have really high strength, really high speed, a lower amount of health and defense the lowest. Another pet I want to have pretty much even stats all around except for maybe health 2k higher. The pet I'm training up now is most likely going to have around 5k speed, maybe a little higher, high defense and higher strength and health. I'm not sure yet about the last.