Having played all the classes and variants, I can tell you that charisma is good no matter what for your main character. It serves a dual role in both conversations and in combat with the potency of force powers.
My personal preference for K1 was Soldier>Jedi Guardian, but there are advantages to other classes and variants as well. For example, in order to gain full access to HK-47's functionality you will need to make your repair skill at some point as high as 17. This is with the help of items of course.
Scout will have the most skills. Scoundrel will be best at talking people out of their money and such.
Jedi Sentinel is similar to guardian, but just don't count on combat quite as much since feat progression is not as fast...it'll be self explanatory soon enough.
Jedi Consular, you're pretty much all about your force powers.
BTW welcome to LF.