Circular Gallifreyan writing, the circular pretty things most commonly known is not their language. It’s the mathematical language (base seven). It’s mostly used for complex equations, rather than writing, because it’s so complicated and difficult to write/read that not even every Gallifreyan can read it very well (so kind of like an engineering language…).Presumably this is why it’s all over TARDIS displays. It’s the technical language. So you probably wouldn’t even understand or care about anything the display showed even if it were translated.
Old High Gallifreyan was kind of like Latin, few really bothered to learn it and it was never really used. (Apparently it’s used in some official writing though, because the Doctor’s ‘name’ is written in it when he’s summoned a few times) Old High Gallifreyan looks very Greek, with some mathematical symbols thrown in presumably because Gallifreyans are kind of math geeks. The Doctor (and presumably River Song) uses it fairly often because he’s like that geek who writes in a dead language to substitute for pig-latin code in class notes.
Modern Gallifreyan, what is (was) usually used during the Doctor’s time looks more like Tamil.
Now go incorporate that into your fics and whatnot.