I was the same until about a month ago. Ive done all of Crotas End now, and half of VoG. Both were incredibly satisfying to do, and rewarding obviously. Try and get in a fireteam, explain you are a n00b and I'm sure there will be some great people that would relish taking you through. The level design is amazing, and the first time you hit the bridge level on Crota with the plates you will be stunned at how amazing it looks.