Alright, this is how you should start off.
Choose a job for the player, for example: Blacksmith, Cook, Bartender etc.
Now choose what the promotion will give them.
Ok, now onto the event!
For my job, I have chosen: Bartender
For the promotion: Get additional gold. Option to work longer for more additional money.
Show text: Would you like to work here?
Show Choices: Yes, No
When No: Ok then.
When Yes: Great! Come to me when you have some free time, and I'll put you to work.
When come to work~
Alright, get behind this counter and start serving customers!
This is optional, either fade out the screen for a period of time, or you can make yourself behind the counter, and mabye serve a few people. To do this, copy the map of the bar and make a new one, then make events, after time, walk over and order drinks, etc.
After your done working~
Bartender: Great work today! Here's your pay!
Control Variable: Or any other variable. +1
Conditional Branch: If Variable = 10
If so, promote player and make sure to DECREASE 10 From the variable
If the player has worked ten times, then they get a promotion.
Make a new event page and make a switch to turn it on.
Then make the Bartender give you the choice to:
If extra, more pay, or mabye even more exp for the variable.
If you choose to have more promotions, make sure to always after the promotion decrease the variable.
A suggestion I would make is after the first promotion, you need 15 exp to get promoted, then 20, then 25 etc.
Watch a video here (This isn't for a bartender, it's for a police officer role . This was in a game I made a year ago, but I'd figure I'd put it in anyway):