I've not played the xbox version but I assume the mechanics are the same as the PC. The secret to character development is assigning your major skills properly (or whatever they're called), cos the way the experience system works is that you level up by using your major skills, and when you level up you get to assign points to your stats. The mistake people make is to nominate their major skills as the skills they use the most - if you want to be a warrior type then nominate weapon and armour skills as primary, assassin nominate stealth etc. That's not the way to do it, the way to do it is to nominate as a major skill one skill from each governing attribute (so one strength skill, one endurance skill etc), while at the same time making sure that the skills aren't your main ones (so if you want to play as a sword using warrior, don't pick blade as a major skill), cos the number of attribute points you get (up to a maximum of 5) when you level up depends on how much you've used skills dependent on that attribute BUT how often you level up depends on how often you use your major skills, so if all your major skills are skills you use all the time, you'll level up quickly without having used skills dependent on a particular attribute enough to get the fill +5 bonus. And since when you level up, all the enemies level up as well, if you pick your major skills wrong you can end up facing enemies way harder than you because you haven't made the most of the attribute gain per level.
Sorry if that makes no sense at all, I've tried to explain it the best I can
Oh, and luck and endurance are the best choices for favoured attribute, luck cos of how infrequently you get luck points and endurance because hit point gains per level are based on endurance so it's best to get your endurance up as quickly as possible.
Also, personally I liked playing as a vampire at low levels, the benefits of vampirism far outweigh the hassle of having to feed before the final day to prevent daylight damage, so try and find a nest of vampires as soon as possible and get infected with vampirism. If you don't like playing as a vampire there's a quest to get the cure so you're not stuck with it.