After 33 (3 level 6s and 30 level 7s) of your boosted runs it will not matter if you bought it or not, but any more and you will be gaining blocks per run. (so if you think you will run that many times or more by the end of the event, GET IT ASAP)I'm already at lvl 6 and I'm wondering if I should spend 2500 to go to lvl 7 D: Using a booster, I'd get around 150 per heartless, so it's not THAT bad... and I'd be 2500 richer >_> What do you think?
I managed to speed-run with a Blue booster and killed 8 under 5 minutes with my magic deck (3 holy and 3 ragnarok), so I think it's manageable to kill 10+ with a raid deck.
As for for level 8... Just after 34 boosts (3 lvl 6s, 4 lvl 7s and 26 lvl 8s) you will be making more Gummi Blocks than if you stayed at level 6.
As for level 8 vs level 7, once you do your 27th level8 run it would be better than 31 level 7 runs. (again the runs are adjusted for the cost of the level 8 upgrade)
In a situation where you had enough potions and boosters to do 100 runs these would be the results. (I will minus runs for the cost of the extra levels)
If you were able to do 100 boosted lvl 6 runs you would get 120,000 points.
If you were able to do 97 boosted lvl 7 runs you would get 128,040 points.
If you were able to do 93 boosted lvl 8 runs you would get 141,360 points.
You don't have to subtract any costs from those numbers, I already did that by removing runs that would be required to pay for it in the first place.
So in other words, if you think by the end of the event you will have done 34 of your runs it is best to level your radar up ASAP. Though if you are thinking you might only be able to get 33 boosters/runs in total. Yeah, you are best of staying at level 6.