There are some training videos for Golf Croquet on YouTube. In particular we recommend a series of 6 videos by Ian Harrison of the Basingstoke CC in England.
There are also some notable matches on YouTube, both Golf Croquet and Association. In particular enter Felix Webby under Search, and watch his final against Angus Coulter for the under 21 World Championship title in 2017. Also watch Reg Bamford in the World 2018 Golf Croquet Final in Melbourne. For Association Croquet enter Paddy Chapman under Search, and watch his win in the 2018 World AC Championships.