The vowels are generally A as in fAther, E as in Elephant, I as in Igloo, O as in bOther, U as in mOOn.
AE and OE sound something like dAY. If you try making the E sound you notice the shape of your mouth is similar, but we tend to close off a bit on AY, which you don't want to do so much in Latin. Watch the video:
C and G sound hard as in Cat and Goose for A, O or U
CA GA CO GO CU GU
C and G sound soft as in CHips and Giraffe with E or I
CE GE CI GI
This video will clear things up:
The parts of a Latin Mass - you can see the same outlines in a regular New Mass.