In my dictionary its also an expression.
もう少し [もうすこし]: (exp) a bit more, a bit longer
Which makes things a little easier.
Is もう necessary in this translation?
Yes, it's the only word that carries the meaning of "more" in the sentence.
Why is it 大きいメガネ and not 大きなメガネ?
Both should be accepted.
It's because 大きい is an い adjective
It is an i-adjective and a na-adjective, so it can be used either way, just like 小さい
Can mou and scoshi be reversed?
Is this just idiomatic/an expression for "a little bigger"? I tried
but it failed.
That means 'I want glasses that are a little big'.
Does word order matter? I put megane ga moo sukoshi okii hoshi desu. And it was wrong.
My only sin was using メガネは instead of メガネが . I though both particles would be acceptable here, especially out of context (no idea if this was already being discussed or not). How do I tell?
Using the topic particle here implies that someone had brought up a talk about glasses — using that particle implies that it’s the question if you want them or not.
On the other hand, the identificator particle in this case introduces new and important info.