“doing something" vs "by doing something"

Question

Which is the correct form?

1. I displayed financial skills by creating the firm's budget.
2. I displayed financial skills creating the firm's budget.

Maybe "while" can work too?

Answer 1

All there are correct, but subtly different.

I displayed financial skills by creating the firm's budget.

says by what method you displayed your financial skills

I displayed financial skills while creating the firm's budget.

says that displaying your financial skills was something that happened while your were creating the budget.

I displayed financial skills creating the firm's budget.

is somewhere in between the other sentences. It sounds somewhat incorrect to me, but I don't know of a grammar rule it violates.