3/8 will cover 90% of your jig fishing IMO, and I always buy jigs with very full skirts as you can trim them down and pull strands to adjust fall rate and bait bulk. Even changing trailers can help slow or speed up the fall rate. Let water color dictate the color of your jig as well, if it is murky less than 2' visibility go with black and blue or all black or even black and some chartreuse. If it is clear 5+ feet of visibility stick natural colors like green and brown. As far as skirt length I almost alway trim my skirts to 1/4 inch below the hook so they flare for on the fall and at rest on the bottom. And the trailer I like to keep my jigs compact unless the fish are very aggressive, since I only use chunks I don't usually have to trim them but I like to have the claw and just the head of the trailer showing to make it appear as a hidding crawdad. For rattles if I am imitatting a crawdad I have a rattle 100% of the time for swim jigs I never use a rattle. And finally the bite, if it doesn't feel normal swing this is also something you will get a feel for over time and be a line watcher I your line jumps swing, of it runs to the side swing, and obv if your rod jumps swing, hope this helps man good luck and don't give up on jigs, they can be frustrating but they will put some pigs in your hands
Tight lines!