If you want to buy diamonds you can use pay-pal an international and secure way for Internet transactions.
If you don't have and don't want to create one, you can ask your friends, sure someone will have, and give him the money to buy you some diamonds.
And as always diamonds are not only bought with money! You can use your Imperial Hero gold.... Sure it will take you some time to buy 25 diamonds but it's not that hard... If you manage to craft epic/legendary items or have one time craft recipes you can sell them for good amount of gold. (You will need around 7,8 Million)
Also there are story line quests that give diamonds as rewards but they are at tier 5 & 6 ( I am not sure at lower tiers I will see and tell you).
I don't wan to become Hunter for fighting with Guardians.Challange is secondary thing for me...........
Well at next tiers not the challenge but the loot will be more and more dangerous... By loot I mean the ability to attack or get attacked by other players, and the loser lose 10% of his carrying gold and even the currently dug resources (if he was digging when he was attacked...) And at tier 4 some of the towns are not safe places either.