EDIT: Seriously though, make sure they're nice jeans that aren't really baggy, and I'd say some brown boots or boat shoes like YSSMAN mentioned would be fine.
I think a pair of khakis would be betta, though.
Straight-leg jeans or khakis are
KEY to get the vintage look right. I'd go with
Levi 511 or 514s ($25-35) on the jeans, and don't be afraid to get them a little short or to roll them up just a bit. As far as khakis go, take the time to find a good fit, and at all costs avoid cargos with this look. I'd suggest
The Gap ($45 is usually the sticker price) to get a nice clean cut, otherwise, you can occasionally find good stuff at Macy's on sale.
Side thought:
Chords. Seriously. Don't get them with a thick rib, but the smaller, thinner kind. Gray or Khaki would be the best colors to wear all-around, and you can usually get a nice pair of straight-leg ones for $30-50 depending on where you shop. Again, I'd suggest
Levi or Gap, but its different for everyone.
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One more side thought:
You can do shorts too, if you like. Make sure they're a clean cut (not pleated), and truly are shorts. To look "right," they'll need to
sit just above or right on your knee. Anything longer and you look like an idiot. No cargo shorts either... I've got a pair of shorts from Structure that I love to death that do the job, otherwise, it seems like Dockers (no joke) and Gap tend to cater well to that need.