If I wanted to try the typical sweater worn over an OCBD look, what sweaters do you recommend I start out (material?) with and where do I purchase them?
Sweater over the dress shirt look
No tie, just a dress shirt under a sweater, only as formal as a dress shirt / sweater typically is -- Casual to Business Casual.
Climate will be Michigan Fall and Winter, everything from 50°F to 0°F. It will be worn inside in a cool office
I know it's opinion, but I'd like to hear some thoughts. What materials / type are easy to get and look good but not too expensive?
No, he is saying you should only use slim fit shirts and sweaters in this combo. A baggy shirt will have folds beneath the sweater, creating bulges in odd places.
In truth, it's probably just the shirt that needs to be slim fit.