Fantastic question. And let me applaud you on where you are clothes-wise -- sounds like you have a great sense of what works for you. Austin is an interesting place to dress it up and dress it down, because you've got everyone from congressmen to cowboys, and all types in between. A good blazer can look right at home with a pair of boots... it's as utilitarian as it is stylish.
If you're gonna look at one blazer for the season that's different than your navy blazer, parties well with jeans or trousers, and is appropriate for Austin – both vibe and climate – I'd steer you towards this houndstooth jacket. I've got one that's an older model but as you can see from our Instagram, I take it everywhere.
Right outta the gate, I'm not sure there's another jacket that's more capital-F-fall. The English lambswool is perfect for anything below 75 degrees, and I like the patch pockets for a more casual feel. It's our sportyish No. 2 make, with a special 2-layer canvas, so it's lighter and breathes a little better than its more-constructed counterparts like the Nos. 3-5.
Style-wise, make no mistake about it, houndstooth is a lead singer. You'd think it's so loud that it's not versatile, but it is! It's unexpectedly neutral... oatmeal and navy, which if you think about it, is essentially like sand and the night sky put together. And what doesn't look good against those two colors? My guess is that it'll go with a lot of your closet already.
One of our favorite looks would be a pair of jeans with a chambray shirt and cowboy boots, or in our case, ropers, to kinda knock around in. If you want to dial it up slightly, wear it with wheat jeans or khakis with a university stripe oxford shirt, and chocolate suede loafers. And if you pair it with grey high-twist trousers, a solid blue shirt, a club tie and semi-brogues... all of a sudden you're boardroom ready.
Generally speaking, you'll want to wear a houndstooth jacket with solid or small-striped shirts, (avoid checked patterns like plaid or gingham), a striped, solid, or club tie (don't compete with the jacket), and pants of any color as long as it's solid with an in-season fabric (denim, cords, twills, cottons). And for shoes... put 'em on last and match the vibe of the outfit.
And if houndstooth isn't your thing, there are plenty of directions you could go... a herringbone or glen plaid, melange wool or corduroy... or even the brown or green version of our favorite leno-weave blazer. All will look great with five-pockets (and for that matter, with the city of Austin).
Just don't wear with shorts, unless you're Angus Young.