I always flip managers at the beginning of every FUT season - it's not glamorous, but if you use your 100 trade slots and all your coins you can double your coins most cycles during the first week.
I'm basically done doing that now that I have teams and more coins, but a couple of quirks I've noticed this year:
Some of the shiny silver managers have 2% contract boost, some have 0% (very odd)
All the eredivisie managers have disappeared this year - Netherlands managers are in high demand for the first time ever. That also means the eredivisie manager league change might be worth something for a while.
People still pay silly amounts for premier league and bundesliga managers.