Here are some references for Ostrogoth and Vandal coinage.
Warwick Wroth Catalogue of the Coins of the Vandals, Ostrogoths and Lombards and of the Empires of Thessalonica, Nicaea and Trebizond in the British Museum (1911)
Wroth is perhaps the most quoted reference for these coins, though dated (and often wrong), as it was written in 1911. Reprints are cheap and downloads online are available. Often abbreviated as Wroth BMC
Wolfgang Hahn Moneta Imperii Byzantini volume I (1973)
Abbreviated as MIB.
Philip Grierson Medieval European Coinage vol I (1986)
A large paperback covering 5-10th centuries. It has good historical data on the Ostrogoth and Vandal Empires and each ruler. Abbreviated as MEC.
Here are some books solely on Ostrogothic coins-
Michael Metlich The Coinage of Ostrogothic Italy (2004)
Demo Ostrogothic Coinage from Collections in Croatia, Slovenia and Bosnia & Herzegovina (1994)
