You probably want to go with the course of action that can maximize the amount of items you can have at level 8. look at your best purified items (for initiative), refine them up to level 8, and see how many you can do. You might be able to get 3, possibly even 4 if you're lucky. Then use enough med refine after that to use 500 runes to collect more adv runes. Then pause and wait for the next month's refine event and do the same. Hopefully time limited and refine will be combined going forward.