Unfortunately the number of Alliance controlled systems is very small compared to Empire or Federation making it alot more difficult. The profitablilty of Imperial Slaves also adds alot of options for trade in Empire space.
On your galaxy map, switch to "Map", "Allegiance", "population - move both to sliders to the left". This will make the system dots bigger on the map.
To simplify the galaxy map, the Empire controls a huge area of space in the "south" of the galaxy. Almost every system is empire controlled, very few independent systems.
The Federation is everywhere "north" of the empire in colonised space, with a smaller presence on the frontier systems.
Independent systems are scattered throughout Federation space making a colourful red and yellow dotted pattern on the galaxy map.
The Alliance is centered around Alioth and there's a small cluster around Lave.
Unfortunately the galaxy map data is incorrect, it changes randomly each day between the actual controlling faction allegiance and the previous controlling faction allegaince.
e.g. Monday the system is red on the map, Tuesday it's yellow, Thursday it's red again etc.
Hopefully this will be fixed evenually so we can have a clear, accurate view of the allegiance of the galaxy.
To sum it up, the Alliance has grown since launch but it's very difficult to make a route similar to the Empire trade route due to lack of stations.
