I don't know if there is help but i found a way for me. Say you like an army and want a taste. I just build one really fun unit of whatever caught my eye that moment. Makes great small solo battles at home or starters if you want to expand.
Alpha Legion
Thousand Sons
Fists
Pre-Heresey World Eaters
I've done this way.
And the new Squats but i built kit bashed version not knowing they were rereleasing from first edition. So Squats got big in my collection.