Electric guitar...

But they are simple I-IV-V chords for beginners to use. Adding the Em for a fourth chord is simple for beginners. Plus G is a relatively common key for vocals.

Key of A requires a certain amount of dexterity on the A most beginners aren't ready for as well as the F#m.

Using the key of E requires a B chord as well as C#m; again a key most beginners aren't ready for.

Patience grasshopper. The Sabbath, power chords and palm muting will come.....
The grasshopper is not even received his ax yet... LOL.. this carriage is way out front of the horse LOL.