None of OP's examples sound idiomatic to me. We don't generally talk about getting / becoming "smart" anyway (you're either smart or you're not, same as you're either tall or not), and we don't usually restrict the scope of adjectival "smart" to a specific subject (being "smart" implies having high general intelligence).
To a lesser extent, the same applies to "clever" - we usually say He's good at maths rather than He's smart / clever at maths. There's not really a "preferred" preposition for smart ??? [subject] because we don't often use that format anyway.
In short, "smart" (=clever, bright, intelligent) is the wrong adjective. It's better to use something like "proficient" (=skilled, accomplished, expert). And check out this NGram showing that both in and at occur with "proficient".
(For the avoidance of doubt, note that I speak and write British English (BrE), as opposed to "American" (AmE). With color / colour the difference is only in writing, but math / maths reflects what we usually say.)