As a "do everything" style jig - what are your favorite sizes for the Arky jig ? In most cases it looks like you would be fine with 3/8th oz. and 1/2 oz. in your typical craw and bluegill colors?

You betcha.  3/8, 1/2 and I like 3/4 because reaction strikes and getting deep fast.  Also my favorite weight for stroking a jig.

 

I would get black and blue and some sort of brown/purple and some sorta green/orange/blue and you should be golden.

 

Jigs are less about mimicking a specific kind of forage and more about creating a reaction strike from aggressive fish.  Rate of fall and action and profile are your key considerations.  Color in general tends to be secondary but these colors work in all water clarity and all seasons on largemouth bass.

I mostly fish 3/8oz & 1/2oz, but like Pat said above there are days that adjusting the fall rate by going over 1/2oz or down to 1/4oz is key to triggering bites. For colors I only have black & blue, green pumpkin and PB&J.

My "do-it-all" jig is a football head because I spend so much time in rip rap.  I primarily use 1/2oz but if I use an Arky it will probably be a 3/8.  There are some conditions when a 1/4 will catch fish when nothing else will.  Blk/blue and green pumpkin is about it for the colors.  I find the trailer choice to be more important than weight or color the majority of the time, but it's important to note that a "clear" lake in my area is 12-16 inches.  If you fish truly clear water you may have more need to pay attention to color.

Looks like I would be fine with the sizes and colors replied above for an arky jig ... A football jig can also be stroked , and swam too which I had forgot about in favor of other applications (i.e. chatterbait) .