worst case scenario 366 refines to lvl up to 9, then 801 to get from 200/1000 to guaranteed level up (correct me if im wrong, cant remember if wish credit gives 200/1000 or 250/1000). Thats 1167 adv refines that need to be used at once, so you need 335 more to be sure.

Now if you need to use all 1167, you're going to lose one pill, few keys and 40 adv refines (one whole rebate, again cant remember if its 40)

If you decide to use refines now and fail, you will need to use 200/250 - 40 more advanced refines (lost wish credits - what you'd gain from rebate), which is ~4k more coupons.

Imo wait. You can only lose on potential rebate if you get lucky (about 1k value+pill) but you make sure you don't lose out 4x more on failing that massive wish credit.

In either scenario, if you succeed those additional refines will contribute towards your next piece of gear so I wouldn't worry about overbuying them.