i got questions too-(fav sups morg,annie,soraka,poppy) -why does support need support item shouldnt they get their normal build? for e.g. why does support morg not start with dorans ring but with the gold item? -howw do i be useful in teamfights -new to support pls gimme any more tips
Any gol income item is better the earlier you get it, simply because they earn you more gold. Now in S4 gold income items are also made to reap the best early game benefit. And they are, stats wise, some of the most gold-efficient items in the game.
Gives a flat magic damage proc, which mechanically is best early while the fixed damage is still relevant. It also rewards proper play of zoning and harass.
Is great for sustain and passive supports, as it can net you the most gold realistically and heals you for every minion nearby dying. Essentially if you plan to stay ion the lane for a long time, get this.
Not as common of a pick nowadays, but is great for tanks. It has the best way to get early game base health, so champs with defensive portions of their kits (tanks) really benefit.
Also, I will say Poppy does not really count as a support. You can play her bot lane and net your carry kills sure, but nothing in her kit specifically helps out the carry. If it works it works but if I may suggest you practice Morg a lot, as she is the favorite counter to Leona,. who is the most popular support right now in most ranked.
As for everything else that's a large topic. luckily I got you covered! Well, of you don't mind reading of course :P. I've been making a collection of Guide posts during my free time and the link is to my Support [Guide] just in case you're wondering.
Ok, this is me oversimplifying the role in order to easily explain the basics:
Start: [Gold item], potions, green ward, yellow trinket -->Rush: Sight Stone, sell trinket for red trinket once you have Sight Stone
This gives you early gold gain since you will not be last hitting, as well as vision control, still an important job of the support. Once you get a Sight Stone, you can place your limit of wards (3) on the field, and no longer need yellow trinket. Your build beyond this is personal preference. In solo queue, I find building items like 
can work as well, assuming you already have one of these 
and this 
. Also consider 
. [Note: these items are assuming you are an AP support like Annie or even Soraka]
Your job in laning phase is to make sure your ADC can come out even, or preferably, on top. You can do this in a number of ways. Annie usually does this by straight up out-trading or helping to kill the opponents. Morgana does this by catching people in her snare/pool, which allows your ADC to get free farm or harass. And Soraka does this by out-sustaining her opponents. Also viable options: Karma - great harass and disengage; Lulu - popular in mid lane currently, still a great support with good peel and poke; Leona - a great tanky option that all-ins her opponents.
VISION. While this is no longer the huge responsibility it was in Season 3, supports should still ward a great deal. In lane phase, this means warding against jungle ganks. After lane phase, warding is useful for objective control. Learning map-awareness is uber-important (yes I just used uber) in any role, particularly support, seeing as this can save you neck and also help catch out opponents. Is the enemy jungle in top lane? Perfect time to go aggressive in bot. Is enemy mid roaming bot? Good thing we saw him with our dragon ward, time to back off.
These are the very bare basics of support. I recommend reading a guide about support on, say solomid.net, mobafire, or whatever site you prefer. Also look into specifics about each champion you want to play, as knowing specific champion mechanics is important in any role. Not sure about Poppy support though; I've never seen her bot, so I can't really comment on her usefulness. I would guess that would be less a support and more a kill lane, considering Poppy's lack of ally help and CC. Anyways, Good luck!
but i seen karmas do better without support items
