I think anyone can earn Vanguard Marks right from the get-go, regardless of your level, (don't quote me), but you have to keep in mind that each character can only earn 100 each week (with resets on Tuesdays of course). The easiest way to get them is from the Strike playlist, but if you don't mind public event hunting, it's technically better. Now if you are talking about Vanguard Commendations, that's totally different, because you can't earn those until you hit Vanguard Rank 3 and higher. You will recieve a Vanguard Commendation as a reward from the level up package, and you can spend it towards armor and weapons etc. Another issue you might have is that any individual character can only hold 200 total Vanguard Marks at one time (like the 25,000 glimmer cap). Unfortunately, what this means is that even though you can't earn any more marks until you spend some of your 200, doing any activities that would normally grant you Marks counts towards your weekly limit of 100. On the bright side, if you have this issue, but you don't want to buy something expensive like armor, (in the case that you are saving for a Vanguard sparrow or something), you can exchange 10 vanguard marks for 10 of an upgrade material of your choice. Not the most useful thing to do with your marks, but if you would have been losing them anyway, might as well just pick up some material you are short on, allowing you to earn more marks.