Guitar Progress [From A to D and back again]

A and D make a great cadence! (V to I)

You could add an Em chord to spice it up a bit (ii to V to I)
also a G chord to start everything (IV to ii to V to I)

The Roman numerals are the chords in relation to the scale.

So for a D Major scale, you have D, E, F#, G, A, B, and C#. Since D is first it is I; A is fifth so it is V. If a numeral is capital, is means it is a major chord and if it is lowercase it is a minor chord.

I learned a fair bit from tabs (or tabliture), where if you can follow the simple
rule of reading upsidedown (basically take open tuning and see it in reverse
from the way your strings are) and be able to play the notes as they are indicated
by fret number (1-21 or 24 depending on the neck and fretting) 0 Being open, and
then from there each number goes in sequence. Paired with a chosen song you can
learn to play covers based upon hearing the notes and tempo, as well as seeing the
correct notes to be played.
I can still kinda remember mostly how to play When Johnny Comes Marching Home.
Guitar is a lot of fun, when you don't think of it as work.