You could start here
http://www.chess.com/article/view/study-plan-directory
Using chess.com
Sort:
1/ Neither. Don't get sucked into that adaptive/sequential nonsense. After you click on "chess mentor" in the upper right corner you have the option to "view courses". Click on that and make a selection from there. Try some of the beginner courses on the first or second page. They're pretty new and well done with good explanations.
2/ Video is mostly for "edutainment" at your level. Most of the courses are very specialized and beyond your current level. There are some beginner videos you could watch though and to get a taste of how a titled player thinks, you could try IM Danny Rensch's "Live Video Sessions". It will be beyond you but give an idea of the road ahead.
3/Opening principles primarily, maybe the first 3 or 4 moves of some common openings. Tactics are the quickest way to increase your board vision and lessen blunders. The tactics trainer here is maybe too much for you now because it is timed. Try it un unrated mode with the timer off. Good introductory CM courses again on the first or second page when you "view courses". GM Wolff has some great tactics courses that you will soon be ready for but maybe not yet. Do the newer and easier ones first.
There is a whole school of thought that says your primary study should be endgames. They have a point, but not if you're still blundering pieces. Beyond the most basic, you don't need much strategy, but the beginner courses on CM should help. Good luck and I hope I didn't just add to your confusion. 
Hi people.
I'm fairly new to this site and to chess in general, there seems to be a massive amount of learning materials and tools etc. i simply do not know where to start!
1 which lessons are best in chess mentor?.....adaptive or start from the beginning?
2 How do i tackle the video lessons? there are so many!
3 openings, tactics , endgames strategy! what do i try to learn first?
i would love to hear any constuctive advice
many thanks