What to get from mysterious sale

Hello guys I came here for some advice regarding the mysterisou sale because I have a hard time deciding what is the most optimal things to get. I am super close to nirvana like 2 transition event rewards away and I already know the most important recourse will become star soul mats. I have like 11k starygemes but basically ftp and want to maximize my rewards. If you are in the same situation and you are chasing star soul mats and or transition mats what would you get from the event and do you think it is more worth it to spend 7500 sg or 3750 sg also if it is relevant my grimore is lvl 109 and I have 5 enabling infusion stone