Really strong item, if you choose to go the doran build, get 2. It helps you survive and have enough mana to spam your spells. Always strong on AP carries.
A Must on Zyra... no matter what. Really self explanatory, she is an ap carry.
Strong item, good against double AP carry, or ap carry and magic damage dealing jungle. Situational.
Situational, strong sustain, strong laning phase, helps you farm.
You must buy this item for your damage no matter what. Either get it after the dorans, the rods, or the abbysal. If you go dorans, you can build into abyssal then dcap, or dcap after rods or dcap after dorans. A MUST GET.
A Must on Zyra, she is all damage, you need this item.
Zyra has no built in escapes in her skills, this item helps her survive late game, you need to buy this item later on. It helps against dives.
Very situational, get this if you need sustain... so you buy this when you're dealing against poke essentially, so you can poke back and heal TA-DA
Situational, but you buy this item against several melee champions that dive you because it helps you kite, or you can just solely depend on your hourglass.
Situational on ALL champions, very self explanatory... good against supression. Buy it against suppression champs. ( URGOT)