1. Weedguards can be any lenght you want. I use to cutt the off down to the height of the bend of the hook. I got hung up a lot so I quit cutting them off. I don't do anything to them except when in brush I spread them.
2. Starter kit for jig tying. I don't really think there is one. You have to decide what you want to make and then get it. If you don't want to make a big plunge then buy some precast jigheads (painted or unpainted) and skirts and then put them together.
If you are going to go hole hog you will need a way to melt the lead, some lead, some hooks, and a mold. Do-It probably can fix you up with what you want.
3. Kit for powder painting. It can be as simple or as complicated as you want it to get. I started out with a candle and 1 2oz jar of white paint. I'd heat the head and swish it in the paint. Over time I have built a fluid bed, collected 20 some colors of paint and heat and cure the heads in a toaster oven.
So what I think is you will have to decide what type of plunge you want to make and how much you want to spend getting into this venture. It can be for a few bucks buying precast heads or you can spend several hundred getting all the stuff for a first class operation.
Good luck to you. It is a very fun pastime and way down the road you can save some money but that first jig sometimes costs you over $100.