My $0.02 as a support main.
When to buy each item...
Relic shield: you are a melee support who's abilities are more geared towards all in engages or hard peel, not so much general harass or ability spam. Income level earned from this item is moderate, but is made up for with raw tank stats (health cdr and shield) when complete.
Spell thief: you are a harass bassed champion aiming to completely dominate your lane early. This items income varies wildly based on your success in lane, if you lose lane this is easily the worst support income item. If you win, it just gets better the harder you are winning.
Ancient coin: you are a champion that spams abilities or has high mana costs, but not really looking to go ham in lane in most cases. Favored by enchanter supports due to mana regen, and the more mana missing the more is restored per mana pickup. This is the safest support item and in an even lane will provide the most gold compared to other support items, if you lose your lane, you still get the same amount of gold as you would if you were winning, making it a better option than spell thief in most cases.
Imo if ancient coin gets a nerf, it needs to be to the mana regen earned from the mana drops, it should be flat mana restored not restored based on % missing mana. This is why enchanter supports are so popular right now (as well as ardent censor but that's another issue)
before I get anything else and while I have to eat AA's to use my stacks and after lanephase hope my teammates will let me use my stacks I have noticed that by the time I get to 1k gold income ancient coin has 1500 gold income. Why does Relic give 2/3 goldincome compared to Coin? I have played against Brand and Lulu sup and they all are getting Coin. The ones that go for Spellthief are even in a worse position incomewise because I have noticed they have roughly 50% of ancient coins income.
