First here is the basic chord structure of the blues:
A7
| / / / / | / / / / | / / / / | / / / / |
D7 A7
| / / / / | / / / / | / / / / | / / / / |
E7 D7 A7
| / / / / | / / / / | / / / / | / / / / |
What you will learn (if you keep playing and studying the blues) is that this is a real basic progression of chords within the blues and you can create many, many variations on chord choice and position.
We can use the A minor pentatonic scale for soloing over this progression. We can also use the A Blues Scale. Here are examples of those 2 scales:
A minor Pentatonic:
A Blues Scale:
Playing the blues becomes a sort of puzzle in which the pieces can fit in a number of places. This can lead to near endless variations on what you can play and how you choose to express yourself.
Here we scratch the surface...