Back when Gorkamorka was released White Dwarf, issue 214 I think, ran several articles on the game (how surprising!). One of the articles was a rather good four page piece that is essentially “starting a basic ork mob 101”, written by Andy Kettlewell.
It covers stuff like allocating resources, purchase priorities and some basics on assembling and painting a mob.
Admittedly the painting isn’t excellent and the models look tiny compared to modern orks, but the principals hold true and the vehicle converting stuff isn’t bad either.
I’d say that if you’ve played one of the similar games, such as Necromunda, it’s an article you can safely live without. However, if you’re feeling a bit overwhelmed with everything, it’s an excellent starting point.