Hint: Play as Cyrax easier:
You would have to have at least 462 Ruby Koins and open Krypt PD (to get 1056 Platinum Koins ) and get the rest of 3003 needed to open CN for Cyrax. You can get extra Platinum Koins in the following Krypts: FV (83 Platinum Koins needed for 243 platinum Koins); PK (157 Platinum Koins needed for 475 Platinum Koins); WS (44 Onyx Koins needed for 165 Platinum Koins); and NG (63 Sapphire Koins needed for 252 Platinum Koins).