All you need is vanguard rep 2. Vanguard 3 is for weapon and those you will get from drops. Once you have that buy the best armor for your class minus the exotic piece you get from Xur for strange coins. You will shoot to 27 or 28 very rapidly.
Max out your exotic armor with shards and then try to get raid armor. I was stupid enough to max out all the vanguard armor before realizing you need raid armor for level 30.
Daily level 28 and gold public events will be your best friend. Only real way to get shards outside of the vault of glass.
You don't always get the right weapons from drops. Relying on the game to give you weapons is folly. Your best bet is buying what you want from venders until you can buy stuff from xur with strange coins or get exotic bounties. Weapons like Shadow Price, Vanquisher, Grim Citizen don't often come from engrams. Every time you rank vanguard past 3 you have a chance to get items as a reward through the postmaster. I've gotten a legendary scout rifle, & the devil you know hand cannon that way. I've never gotten weapons worth anything from nightfall, weekly, or vanguard strikes. I have seen people get exotics that way but it is not a good idea to rely on that. The only weapons I've received as rewards came from the Vault of Glass. The RNG in this game is unreliable at best.
My Vanguard is rank 13 because I always do my daily bounties and daily story and max my marks each week. I also maxed all my gear as I went. I had legendary stuff and maxed it, got an exotic piece and maxed it, got raid gloves and maxed them, got raid helmet now and am working on maxing it. The extra defense is important. Your weapons are important, You should try to get Legendary weapons and level them. Don't rely on the game to give them from drops. If you have to, buy them. Guaranteed legendary stuff is better than sitting on Rares too long. If you max your marks weekly which takes almost no effort, you can buy a full legendary set in about two weeks and a legendary weapon in about another week. I've seen people complain about not getting stuff from drops when all they have to do to progress is buy some legendary stuff from venders. You can hit level 28 from vanguard, faction, or crucible gear.