inb4 ladyonthemoon gives you all a withering look for saying unofficial patches are essential (but they are).
I see you have the strategy guide. It's nice if you want to learn the basics or to help if you get stuck somewhere (though in general opinion, http://www.uesp.net/wiki/Main_Page is better for that), but I advise against looking up quests and locations. Skyrim is jam-packed with big and small things to discover and it's really, really satisfying if you find them on your own. Get lost, talk to people, check every nook and cranny, don't follow a walkthrough. Exploration is one of the strongest points of this game, so spoiling its secrets is counterproductive.
You don't need to hurry with buying the DLC, they have a lot of content meant for high level characters. IMO Dragonborn feels most natural if you start it after, or near the end of the main quest. But DG and HF integrate some neat features with the base game, like house building, arrow crafting, werewolf and vampire perks etc., so you may want to get them first.