GWX Renown?

I was just wondering if anyone could give me the low down on how GWX renown works because I had a somewhat succesful patrol (1 ore carrier and one medium merchant sunk) and only got like 96 renown from it?? I really want to get a type VII bad too and I need to find a way to get alot more renown each patrol. Does attacking war ships give you more renown? and where could I find some warships in 1939?? more specifically something big. like a cruiser or battleship? or carrier