I think dressing yourself well is very similar to cooking. It's about individual pieces making something great together. Find your taste.

Pants: there's not a lot of different types that look stylish but there's a ton of variation. Jeans aren't inherently bad, although I would try some more slim fitting pants. I have some neat black / dark blue pants and some caramel pants. I'd definitely try some accompanying belts.

Upper Body: ever tried some casual button-down shirts? They require some work ironing them, but I really enjoy wearing good-fitting button-down shirts. Also, you either ENTIRELY tuck them in your pants or not at all. The former also looks way better with a belt. I've seen people who put their shirts in their pants only on their backs and it just looks weird. T-shirts can be pretty stylish too. I have multiple colors of these.

The most important advice is to try stuff out. Go to a store that you think is stylish and try all the clothes on, even though you don't think it'll suit you. And no, nobody at the store cares that you only buy one of the ten thinks you tried on. Do ask them, they often know what works together and they haven't seen your previous wardrobe much.