Galerius as Caesar     25mm aVF follis of Thessalonica     Sear 3709    V.M. 29     RIC 24b
GAL VAL MAXIMIANVS NOB CAES - Laureate head right
GENIO POPVLI ROMANI - Genius of the Roman People standing l., holding cornucopia and pouring wine from patera
Minted in 303 AD while Galerius was serving as Caesar under Diocletian.  Two years later he was raised to Augustus when Diocletian retired.

Galerius as Augustus     24mm VF follis of Cyzicus     RIC 59
GAL MAXIMIANVS P F AVG - Laureate head right
VIRTVS EXERCITVS - Mars advancing r. with spear, shield and trophy over l. shoulder
Minted in 309 AD shortly before illness began his slow decent into death.  A great portrait.

Galerius as Augustus     25mm VF follis of Nicomedia     Sear 3718     RIC 54a
IMP C GAL VAL MAXIMIANVS P F AVG - Laureate head right
GENIO AVGVSTI CMH - Genius standing l., patera in r. hand, cornucopia in l.
A coin of the same period as the one above but showing a much older Galerius.  I have no idea what the abbreviation CMH stands for on the reverse.

Posthumous commemorative of Galerius     23mm gVF follis of Ostia     Sear 3723    RIC 31
AETERNA MEMORIA - Hexastyle temple, doors ajar, eagle atop
Minted by Maxentius sometime between Galerius' death in May, 311 and Constantine's defeat of Maxentius in October 312.  Maxentius gets my award for all-time best hypocrite, what with all the commemorative coins for people who had wanted him dead.   Then again, maybe it was just a way of saying "Nya, nya, I'm alive, you're dead.  I win.". 
This coin is dedicated to Galerius as the "Divine Father-in-Law of Maxentius". (Maxentius had married Galerius' daughter by Galleria Valeria, Valeria Maximilla).  ex Harlan J. Berk