League of Legends (LoL) Question: Specific support's first gold income item?

Honestly you should just read guides for the champions in question because well, that's what they are for right?

Anyway, on leona always start relic, soraka spellthief and don't play support nidalee at all. Your team will hate you for doing it.

If you insist on playing it, I'd go for spellthief because it of course also procs on AA's.

If you are playing aggressive mage support ( Zyra, Karma, Nidalee) I'd say that you want Spellthief's Edge because of its increased damage and gold gain when you are attacking enemies.

If you are playing passive/tanky support you probably want to go with Ancient Coin most of the times because it doesn't require you to go close to the minions the get harassed and it doesn't need as much co-operation with your teammate as Relic Shield does.

I can only say for Soraka: going around attacking people as Soraka is usually at best a rather poor idea, so just stay in the back and outheal everyone.

Most melee/tank supports go for Relic Shield.

Ap heavier/poke supports go for Spellthief's Edge.

Worst start Ancient Coin only fits few supports that play passively and have sustain to take advantage of mana regen. Such as Soraka, Janna. Some supports like to alternatively run Ancient Coin like on Thresh because Spellthief's Edge doesn't fit him and only those certain of their farming ability/premades run Relic Shield. Ancient Coin's upgraded form talisman benefits Thresh a lot so that's why players run coin on him. It's not recommended to start with it tho as it doesn't give anything to lane so most players just start Doran's Shield or Ruby Crystal and then take coin.