Learning Greek

I'm making a monster name generator for my game. Traditionally video game monsters have Greek names. So I need to know basic Greek inflection rules to turn noun into an adjective, suitable for monster name. For example greek word for gold is "chrysos" (yes, Jesus Christ got greek surname). Now would "chrysis" be the correct word for golden? Now Google Translate claims it is chrysafenous, but I'm dead sure the ancient Greek word for "golden" is "chrysis", and google translate also translates "chrysis" as "golden". WTF is with that chrysafenous?

``Gold'' in Ancient Greek is χρῡσός (whence Latin chrȳsos, of which chrȳsīs is the dative or ablative plural), and the adjective form was χρῡ́σῐνος. In Koine it became fashionable to use the diminutive χρυσάφιον instead, which gave rise to Modern Greek χρυσάφι, whence the adjective χρυσαφένιος. χρῡ́σῐνος was used alongside it well into Medieval times.
(Note that <υ> was /u(ː)/ in pre-Classical and non-Attic Classical Greek and usually /y(ː)/ in Classical Attic. The Romans usually spelled it <y> in their borrowings and also usually pronounced it /y/; it didn't become /i/ until much later. Likewise, <φ> didn't become /f/ until post-Classical times, so don't transcribe it as <f>; the Romans knew /f/ as a phoneme, and they transcribed <φ> as <ph> for a reason.)

>>2
It's not that books on Greek cost a fortune, it's that books on linguistics do. You don't need that, you need a language course. The single best one is Mastronarde's Introduction to Attic Greek, which you can get on Amazon for like $3.
The usual justification for linguistics reference works costing so much is that you're supposed to check them out of your university library for free. If you're not currently attached to a university, though, you're fucked, and it is indeed unconscionable. FWIW, the most I ever paid for a book was €250, for an etymological dictionary of Latin.