Does anybody know how to aquire 1 star war cards?

For your hero characters you can Evolve them at certain levels with Combat Manuals. These are earned in the campaign mode. You need combat manuals I (1 star) for the evolution at level 10. Then you will need Manuals II, III etc. at higher levels. You get all of these from the campaign as you progress.

You can also get manuals from occasional rewards or redeem codes.

Do lower campaign levels.