I am assuming you are talking about the kits that have the wort already prepared in a bag, and you have had to place in fermentation vessel, and add the yeast?
My progression went from a 2 liter pop bottle kit I received as a gift, to Coopers canned kits, to playing with hops and steeping grains added to the canned kits, to me making my own recipes with grains, hops, and either liquid malt extract or dried malt extract. I started two years ago and have 40+ brews logged. I am still learning constantly. My advice is read, learn, apply, and read, read, read. This forum has helped me immensely, and brew,brew,brew. I have had only one batch I had to dump, and that was laziness on my part. Good luck, its very addictive.
Only problem I have is I cant drink enough of my brews. I want to keep brewing, but pipeline is at max capacity(4 kegs, and 2 fermenters.