Unlike popular belief, guides are not mandatory in World of Warcraft. You should be far away from it; a person could occupy themselves with solo-oriented content for years on end. Joining a guild is a personal choice which should reflect on the sort of play style you have and/or would like to have. Above all you may take your own motives into consideration and then find a guild that matches them closely.
Fourthly you should improve your overall playing experience by immersing yourself in World of Warcraft lore. There are many sites out there who publish bios, plotlines and other extraneous information. It is for sure that knowing what color Kel Thuzad's eyes are might not help you push hotkeys any faster, but little details like that will help you get in to the feel of the game.
Lastly you should worry about number crunching after level 60. To be honest, levels go by so quickly from questing now that fine tuning and tweaking your character is next to pointless unless you plan to do PvP in a particular level bracket. All your equipment will be replaced over and over again until it's time for the endgame (post level 80).
First and foremost, when it comes to starting out with a character, you badly want to play rather than what might be needed at the time. There is nothing frustrating than leveling a new toon and then realizing you don't necessarily enjoy what is required to play it. Remember, it's you purchased the game and it's ultimately your money every month.
Secondly you should find mods and addos that work with your play style. There are plenty of downloads out there that address whatever concern you might have as you play through the game. Do you need more bag organization? There are bag mods. Do you need better pricing on Auction House items? You can grab an Auction House mod. Do you think that the default user interface is clunky? Many custom UIs are out there for the asking. Even something as simple as quest research - there are indeed quest helpers available.
For the most part, PvE raiding works for some, a more casual approach is better for others. It's all about the amount of effort you would like to put forth in developing your character(s). There is no wrong way to go about it - whatever works for you is fine.
Thirdly you should figure out what kind of players you are by the amount of time you have to spend playing World of Warcraft. Getting to know what play style suits you will be helpful in choosing what circles of people you play with. Once you find folks who share a similar viewpoint and play style, you'll find your experience far more enjoyable.