Stick to levelling Vanguard, since the vanguard marks you need to buy gear are much easier to come by than crucible marks that the vendors take, unless you PvP a LOT. Looking at your medal score I would guess you don't PvP very often. I don't either, so when I was levelling up the Vanguard armor was much easier for me to get. Run as many Lvl26 Roc strikes as you can, as there are decent drop rates for legendary engrams (one every four or five strikes in my experience) and you can get legendary armor from those as well if you're lucky. Plus each Roc strike gives you I believe six Vanguard marks and they add up quickly so when you do rank up your Vanguard it's easier to buy gear.