Welcome! There are a lot of posts here regarding late 13th century and 14th century, maybe give them a look and feel free to join in or relight a discussion
If your kit is going to be late 13th- early 14th, The armor you should be looking for is this.
That is; covered in mail armor from head to toe, then a coat of plates, knee and elbow caps, cuisses, and the shoulder decoration known as ailettes. As well as a Dargen, Madeln, or Sugarloaf style bucket helm.
I would also recomend starting with a soft kit first, basic clothing, then padded armor, then steel armor.