Raminus Polus, the mage questgiver for Apprentices upwards, tells me that we need to talk about advancement when I click on tasks, and that I'm not ready when I select advancement.

After finishing the staff quest (the first one he gives you), I used setstage to start Ulterior Motives (where you talk with the count of Skingrad), but no luck - his dialog won't change, and he won't promote me to evoker like he's supposed to.

Any advice on how to fix this or reset his dialog options?

I had a problem like this once and I was tearing my hair out. I finally discovered that it was because I was using Choice & Consequences. Are you using this? If so, the mod won't allow Raminus to advance you until you've donated a certain amount of ingredients to the Lustratorium, Necomancer robes to the practice room, soulgems to the Chironasium etc. If you really can't wait you can get multiples of the items through the console, just look up the item codes for what you need.

Ah-ha! Thanks.

I've made sure to turn in everything but soul gems (the guy doesn't recognize the presence of filled common soul gems in my inventory). I have all apprentice certificates, and one journeyman and one expert. Yet Raminus still gives me circular dialog on advancing and tasks. Is there a console code I can use to promote myself?

Try typing Player.SetFactionRank MagesGuild, 3 in the console. That should get you to Evoker rank. Be sure to include everything in the highlighted text.

For some reason, the "tasks" option has disappeared from Raminus' menu. I've advanced to Journeyman, but I'm can't officially complete the quest.

I think it has to be the soulgems, then. Advancing quest stages and ranks via the console won't give Raminus the right dialogue options. IIRC, wasn't it empty soulgems the Chironasium wanted? In any case, check and double check you've given in everything you should to the departments, and if it still doesn't work, I guess you might have to deactivate the mod

IIRC custom filled soul gems can't be recognized by the game if a script checks for a special soul gem type with a certain soul since they're different from the pre-filled ones you find. Most likely he will only accept already filled common soul gems you find in the game world (in chests etc), but not empty soul gems that you filled yourself with soultrap.

EDIT: Try player.additem 382D6 [Number of Soul Gems to add] to add pre-filled common soul gems with common souls to your inventory and see if he will accept them. Like player.additem 382D6 5 for five soul gems.

It's also generally a bad idea to force advancements via the console because the scripts to move things forward may be doing more than just setting a stage. They may be altering variables which then enable new dialogue conditions, etc. It's always best to figure out what the mod wants from you and do it the proper way.