DrakeAldan
Follow the rules!
When you have a good read.But what's your opinion on when to do it, as in, how frequently?
A step is for punishing predictable verticals.
Backstep, punishing predictable fast moves (which are generally short range).
JG and GI are for punishing predictable rhythm. JG is harder to do but costs no meter, GI is easier to do but costs meter and only forces a mixup.
When you throw an attack out, and your opponent is the type to immediately retaliate, you can start abusing JG. Or, if your opponent is continually attacking and rushing you down, you can JG to stop the momentum.
If you don't know your opponent's rhythm and you JG attempt at disadvantage, you're just guessing. It's not totally risky, but it's not the smartest thing, either.
If your opponent varies his attacks or rhythm, you'll get smacked. So, you shouldn't be using JG all the time. It is a defensive option, not THE defensive option.