Finally had some time yesterday to try out this out online on XB One. Great game it's a lot of fun. Did pretty decent starting out.
What are some go to guns to unlock?
Assault should go for the Model 10 Hunter shotgun. Even the starter Trench shotgun is decent but a shadow when compared to the Hunter. Then the rank 10 gun, Hellregiel, is probably the best gun in the game.
Support have a few decent ones. I liked the MG15 but the BAR is also very popular. I just unlocked the rank 10 yesterday and it's pretty beastly also.
Medic, all the guns are pretty decent but the Mondragon Storm seems to be a go to gun.
Sniper, the gweher 86(?) infantry is good and so are most of the bolt actions. The Henry martini rank 10 rifle is a 50 cal and it's fun to use as well.