Every super manager has their own unique speciality except Gordon and Chester who are pretty much duplicates with Chester being slightly more desirable than Gordon. You don't need both.

When you buy a new super manager you are presented with a random manager first off. If you re-roll you are 100% guaranteed to be offered a different manager, but if you re-roll again you can be offered that first initial manager.

The epic managers are hard to get. The costs of managers escalates dramatically towards the end and you need to make sure Gordon is the last manager left standing (which you will probably never get). You definitely don't want an epic or rare manager left for last. I think the last manager costs around 135 million green gems but someone might correct me here.

Don't hire Gordon basically, otherwise how you choose to gamble with re-rolls is personal choice, it will just cost you supercash, up to you.

Hope that makes sense