True chance of achieving "safe" Star levels

[Herby]

1st i never buy stars at 10 gems a pop, so that calculation is way off.
2nd i never said i used them all at once
3rd i know how to play the game and my talents and equipment are decent levels for my power. don't treat me like an idiot.

Let me re-do the calculations.

You should have used those 750 gems that you spent on 150 blue medals during free star friday to upgrade your talents and equipment.
The gain from stars is quite less compared to what you could have gotten had you upgraded your gear and talents instead.
Also, starring only affects 1 hero. Upgrading talents for example, affect all your heroes and is a much better investment.

High star levels are what you could say as "icing on the cake", instead of the cake's filling itself.
Having a high star hero doesn't guarantee success in any way.
Having a high star hero paired with excellent gear, runes and talents gives one a good chance of success.

Looking at your account Greenly, I highly suggest you try getting level 50 weapons or level 30 armor before you foray further into increasing your Star levels.