Op shops are great. I don't have much money so I've always done most of my clothing shopping there anyway. It definitely is a help with transition, though... and weight loss. I've lost a lot of weight this past year, mainly due to health issues, and I'm constantly needing to buy new smaller clothes.
Unfortunately the city I live in now only has one real op shop in town (though plenty of high-priced vintage stores) but it's on my way into town so I pop in a couple of times a week. That helps a lot with getting the good deals.

Lately there have been a LOT of new-looking shirts from one of my favourite menswear shops in there, I realised that they've actually been passing on some of their returned items with flaws. I can sew, so I look over the garment to find the problem (some of them still have the return slip, helpfully informing me) and decide if it's worth it or not. If so... $100 shirt for $5 and maybe a tiny bit of mending, huzzah!
I've also found some great bargains on high-quality men's shoes, brands like Alfred Sargent, Loake, etc. They don't know the value of them.