Before you begin studying the language, make sure you are doing so for the right reasons.
Firstly which "Ancient Greek" are you learning? Is it Attic, Ionic, Aeolic, Arcadocypriot, or Doric? Ancient Greek is a collection of different related languages which were not mutually intelligible or standardized, they have varying grammar, lexicon, and pronunciations. You are about to devote a very long time learning a specific language which might not grant you access to read the texts that you want.
Secondly, retention of a language which you've learned requires access to media in that language, seeing as you won't be speaking it to anybody. It will require lots and lots and lots of media, which unfortunately as far as ancient sources go, you will be quite limited compared to someone learning a modern language which will have movies, music, speeches, etc to study from. You will be limited to a handful of ancient texts.
Lastly, even if you spend many years to attain fluency (or even just reading comprehension), you will be limited with what you can really do with the language. In your case you simply want to write poetry and prayers, so this point is less relevant to you in particular. However if one wants to learn a language to gain access to a plethora of knowledge, do not go for an ancient language (save perhaps Sanskrit or Latin for many scientific documents). There is far more to be learned by learning a modern language such as German, Russian, Chinese, Spanish, Arabic, than there is from an ancient language. Learning a new language is an extremely tedious task, so if you are willing to dedicate an immense amount of energy towards such a goal, I would advise you study a modern one that can actually be spoken and practice with living people. Again this point doesn't pertain to you, but I thought I would put that out there to people who want to learn this language under the presumption that they will unlock new information from it. If you already speak English, then you arguably already have access to the most information a monolingual person could.
I don't say any of this to discourage you, just consider these facts before you begin your journey, as it won't be a cakewalk.
Vira_ said:
also I think in the future it can be the international language as English is currently, or even the only spoken language.
There is no reason for this to ever happen, but if it did, English or Latin are far more likely candidates. Why Ancient Greek? It makes as much sense as picking Old Norse or Ancient Egyptian.
An international language like Esperanto will only come about if Jews decide so. As we're heading, it seems that English is set to become the international NWO language.