Thrift stores mainly, I learned a neat trick recently! Your neck is about half the circumference of your waist, so you can check wether a pair of pants will fit you by seeing if the waistband can envelop your neck. Here's a video

Anyway I like high-rise regular fit pants. Khakis, dress pants, jeans, whatever. As long as they feel like quality, which can be tricky to find because of the people usually running thrift stores being old ladies who pick clothes they themselves like, but it means when I do find something it's pretty cheap. Wish I knew some good online retailers for decent clothes at a fair price though.