Iwith the coke I'm earrings on the put gammon in and see if one can comes up the sides enough? And not two cans swimming over the top? It is trial error like anything scary at first.
Beef joint the same,you could add carrots ,potatoes and beef stock ,couple inches of stock should keep it moist,add some bisto at end to stock if you fancy a thicker gravy. Cook on low whilst pit and turn to high when you get home,while you're doing whatever you do when you get home.
The easiest kind of meals for me are things like beef chilli,as it's just how I would make it on the cooker ,in a pan. Or savoury mince and onions,you could add carrots,potatoes to that ,just mince,beef stock,carrots,onions,potatoes.
I actually prefer things like beef joins done roasted in the oven,it's each to their own.
The baked potato thing always confuses me,I wouldn't dare I don't think,as most machines say "do not use without water" so I never understand the foil/potato thingy.
I think your best bet for a first go would be gammon and coke. I'm not adding veg into mine,I'll do it separate until I've mastered the gammon bit.