When I first started playing I mostly just chased single contacts and ended up with plenty of tonnage. Don't waste torps on small or agile ships, eg, fishing boats, destroyers.
I recommend RuB and SH3Commander for mods (as well as graphics mods of your choosing), dont forget UnRealUBoat - it changes some of RUBs features you dont like to default.
And JSGME mod enabler is very important
