What is a max quality summons

Is it a good idea to spend 300 gems for max quality summons?

Everithing is random and pure luck.From my experience i can tell you there is not a pattern,
I have done bundels like 10 puls and got 2 5* heroes and have done 10x puls and got all 3*
I have done single puls like 300 gems and got crap or on a diferent ocasion(hapend only once)
Got a 4* and bonus round with hotm…
So good luck sorting that out :)))

Thanks for taking the time to respond!!-