Years ago, when I bought my first dual sport, a (now re-sold) KLR 650, part of the deal was a big discount in the store on anything they carried or could order.
The first thing on my list? A proper pair of riding boots.
Why boots? Because riding off road means a high risk of injury to your feet and legs. Although I had been lucky wearing just a pair of hiking boots, I've seen several riders break bones and end up on crutches.
I chose a pair of Sidi Crossfire Adventure Boots - the top of the line, albeit pre-Gore Tex version. Now, years later, I've ridden with these boots all over the country and logged tens of thousands of miles without any complaints. Although not advertised (back then) as waterproof, they've proven to be heavily water resistant.
At $500+, they're my most expensive piece of kit but I wouldn't hesitate to buy them again. They've performed well and proven their value.
Shopping today, there are more alternatives available. I recently ran across this review of Forma Adventure Boots. At $300, a serious competitor. It's worth a read.
Adventure Motorcycle Forma Adventure Review