I have been maining support as my role since I started playing league 2 years ago, and I have learned a lot about the behavior of each champion. That being said, Morgana is the best support I've played to be universal against all champions. (With my build that is).

I see a lot of people grabbing the standard build with icy ghosts, and sightstone, but this isn't successful really unless the enemy team is just too tunnel focused. Talisman of Ascension is a more beneficial starting item as it grants you more gold each minion death (even more with my masteries), boosted movement speed passively around towers, and an active ability that can act as a sivir ult and last LONGER than the icy ghosts slow, and can either save your team or secure kills. This along with the early Armor and mana regen, it's almost never the time to go back home because you are constantly growing your mana back, and don't take much shredding from the opposite ADC. This is amazing because you can keep up with your ADC's money gain without having to take many minions at all. This is beneficial so that you and your ADC are not too far behind together and can team up with your stats, as many supports are too far behind on money to effectively help the team.

The main goal of Morgana support is teamwork. But that should be every league game right?! Yeah we all know the toxicity and how hard it is to have teamwork, but just focus on yourself giving teamwork and if you lose, oh well. The next team may team with you better. This being said, the entire guide should be played off of trying to help other players. Speed boosts for them, shields for them, wards for them, stuns, slows, and really good poke after you have Rylai's.

**Note: Talisman of Ascension is beneficial for securing your ult as all champions in the ring must stay in the ring for the second stun. You need to be fast to effectively keep her ult.

The playstyle I typically take with this build for Early Game:
Poke each minion once to make it quicker for your ADC to take the CS, taking two hits per minion will be wasting time and more than likely the ADC won't capture the gold. Poke, run, poke, run. If there is a champion, get on the other side and play a "you can't catch me" game around the minions. Then, when the enemy minions are starting to clear out, make your move. Predict where they'll run and stun. If W is up, use it. Get that damage output. Not main priority, though very important. Always run away from possible ganks or rushes.

Mid Game: (15-30 minutes in)
By now I should have Boots of Swiftness, Talisman of Ascension, and be working towards Rylai's if not already have it. With this itself, it's very hard for people to kill you. Boots of Swiftness is the best combination with the Talisman, because you gain around 450 MMS just standing next to towers. Any skillshots? Just walk away. Use your E as a Lux's slow effect as well as damage output, and while they're slowed, Q them more accurately as they can't run away. If there is a gank coming, ping your ADC to run, and immediately activate Talisman and shield them right away. This will allow them to block any CC coming in as well as get away as swiftly as possible. I almost always have my bot lane pushed into the enemy tower, and almost always get away. Sometimes bad luck can make for a successful enemy gank. Focus on pushing now that you have these three items. Harass until the enemies die, push towers, rush dragon, midlane, anything you can do to contribute even more. get the upperhand, and with your massive MMS, you can roam with ease with your teammates.

Late Game: (30+ minutes)
By this point, you should have the upperhand and not have died much, if at all. Start thinking of situational items. If you are seeing that top and mid are being pushed too hard, consider banner of command, or ZZ'rot and make use of your MMS to use these items to the best effect.
I did place Abyssal Scepter as a necessity item, though in extreme cases it's not very important. Abyssal Scepter is important because AP champs are bursting a lot, and your Talisman gives you Armor as it is. The Talisman's armor should sustain you long enough for you to escape any unnecessary deaths. If the enemy team is hard on AD and have the upper hand, consider more towards guardian angel or Deadman's Plate. These are extremely useful because you gain a second life, (helping you stay the OP support you are) or the massive MMS you get from Deadman's and extra armor. I almost always get Abyssal Scepter because AP champs are more popular in Season 6, though may change next season with the Assassin's changes.
If your entire team is looking good, or mostly good, start considering AP items such as Rabadon's or Luden's Echo. Luden's will give you more MMS, and Rabadon's will just make you an OP mage, straying off the image of a typical support. If the enemy team is super tanky, get Void Staff last item.

If this playstyle does not fit you, do not force it. You have to be attentive in running away and pulling off tons of CC. Don't go alone anywhere, and don't get caught. If you have a weak squishy mage such as Soraka or Sona or Karma alone while the rest of the enemy team is across the map and non-threatening, go ahead and secure a kill with your massive AP and CC. Other than this situation, you should never be attempting to get kills. Squishy Vayne can still hit you hard and kill you.