I'm one of those crazier AP-or-straight-tank supports out there. Yes, i'm low elo and rank, yes i mostly play normals. I don't usually get Sightstone regardless of which support I play, instead i just buy straight out the wards i need until i can upgrade my yellow trinket. No, i don't use the red trinket. Why? Because from what i've seen from observing games and endgame statsat my elo chances are low of scrapping more than 5 wards in any long game because the enemy team doesn't usually ward half as much as they should themselves, when in exchange i can ward the map at full capacity without wasting an item slot.
As far as money goes, you won't ever see me voluntarily touch a minion until farther in mid-game where i either just snag a few here and there to increase my output or have to stop a push because everyone else is busy with other often not actually as important things. I am of course extremely aggressive in my usual gameplay patterns, so usually with a Frost Queen's Claim and enough assists which i sell at a net profit every time i can sell it, by 30-40 minutes i'm usually among the richest players on the field in a good game. My average Sona game that lasts around 40 minutes would have me have around 50 CS unless i was playing mid Sona.
As far as supports impacting games, i lean on the full AP side of the spectrum (on AP scaling supports like Sona who has sweet passive and W/E scaling, and don't forget scaling up her Q gives everyone some extra damage for free) when comparing the AP/support itemization. This of course doesn't apply to all supports and usually not much to tank/utility supports, but i find tank and support itemization to be very similar. I really love being able to heal practically double what a support support would. Double the speed ups, slows, and everything else. And a few of them can actually 1v1 carries, or at least hold them off. I always find it really annoying when an ADC in mid game pushes your turret and ignores you while destroying it because you aren't a threat. As AP support, you can fight them back, scare or hold them off, or even kill them if an opportunity arises.
Time for a little story, yes? Yesterday my Vayne carry was going 9/1/4, and I was going 3/0/11 as Sona. Yes, I think getting a few kills when your ADC is already fed, or when you have a safe opportunity your carry can't take is totally fine, so long as the carry remains the focus of your play By then, I was fed enough I had my boots, my Frost Queen's Claim and my favorite, Lich's Bane. Our mid lane Yasuo was struggling against an Ekko, going 2/3, and Jungle their and ADC were mid as well. My ADC and I went to join in, and when I arrived I poked Ekko for about half his health while he was retreating. Two pokes later on the careless Ekko and he was dead, and my mid laner could catch up his farm as the enemy jungler and ADC couldn't oppose a 2v3 in these conditions. We got a good push on and took their mid turret. Before I entered lane, Yasuo was half dead, when I left, he was full health and farming for his gold. The kill didn't happen because I was greedy as much as it happened because the Ekko was in range, being careless, and both Vayne and Yasuo were too far away to act. I think that being able to feel like an active threat besides CC to the enemy team is a nice bonus to the support role. As far as I was concerned, my support job was accomplished, and I think I even dropped a ward there while going back to bot lane.
Is this gameplay type perfect? no. Do i love it? yes. Does it work? yes. Does it have flaws? yes. Hell, also yesterday i went 0/10 to a Blitzcrank because i couldn't be damned to learn my lesson and watch those god grabs when playing the game's squishiest champion. I do that too sometimes, but it's pretty rare.
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FAR more powerful. take 
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, and then for dmg support often a 
) more gold would allow supports that need that extra item to be powerful, to be way stronger and wayyy more gold efficient.
like you suggest their, you will find as you are, that you don't finish your build till 45:00-50:00 mins. AP builds are expensive and it take mid lanes a long time to finish a full AP build. Support items are very cheap for that reason. You get less gold and you spend less gold. personally, I think that supports are doing fine right now, item wise.
is core on morg, but many poeple also build things like deathcap or morellos on her which are exspensive items
are great at helpping supports get the money they need. Learn to use them effectively.
all in all im not asking riot to make us extremely important i just don't like looking at the same damn end game items of Sight stone Generic supporting item Aegis boots,