I have 19,396,125,000 Beri (Tentatively, if Ren doesn't make activity I will have ~500m more, so I have enough beri to make the purchase regardless - will update the final amount if that's the case.)
Buying 100x 250 exp for 16b (25,000 exp)
New Beri Amount: 3,396,125,000 Beri
New Exp: 638,532 + 25,000 = 663,532 (Level 100)
I now have bought 775,000 experience, still 160m/250 exp.
Buying Devil's Will for 200,000 experience.
New Exp: 663,532 - 200,000 = 463,532 (Level 100)
With this, Akira is probably maxed out, in terms of monetary purchases I guess.
EDIT: New Final Beri: 19,878,625,000 - 16,000,000,000 = 3,878,625,000