Hoard all advanced refines, make use of the refine rebate to make sure you can max out to level 10 in 1 go. Do it 1 piece at a time.

Make sure you have enough to max out each level (in case you get unlucky) before getting the level 7, so stop at 6 and save enough to max it out to 10.

If you fail to reach the max level during the event, it will then require you to spend hundreds of refines extra. Example: lvl 9 -> lvl 10 has a max 1000 attempts. If I remember correctly the refine rebate from going to lvl 8 -> lvl 9 is 200 blessing? So if you fail, it will take you at least a few hundred more attempts to max out that level. At 38 coupons per at retail price, that mistake could cost you up to 7,600 coupons/ingots to fix, per equipment.

I messed up early in the game before I really understood the event, so now I'm stuck in advance refine hell. I'm forced to save up only advanced and enough of them to max out all my equipment. And it's taking forever. So listen to my advice otherwise you'll be SOL like me.