Green staples? Cards I always suggest? MOAR RAMP!! Since you have many ETB triggers I would add in some creature based ramp first.
Wood Elves is a favorite because he can grab
Breeding Pool or
Temple Garden to help fix mana, if you are already fixed he brings a
forest into play UNTAPPED.
Farhaven Elf could grab any basic, tapped unfortunately.
Sakura-Tribe Elder can also grab a tapped basic.
Fertilid can be good, especially with the
Archangel of Thune.
Oracle of Mul Daya gives extra land drops and lets you play lands from the top. I feel the combo of ramp and deck thinning is worth your opponents knowing what you draw, but many disagree with me.
I put a huge amount of ramp in every deck I build, so green means
Nature's Lore and
Three Visits go in for me, for the same reasons as
Wood Elves.
Kodama's Reach and
Cultivate go in if I have things giving me extra land drops (again this is both ramp and deck thinning). Multi-color green decks also benefit greatly from
Farseek.
Besides ramp,
Beast Within is great.
Green Sun's Zenith is useful whenever you draw it. It grabs
Essence Warden or
Birds of Paradise onto the field for 2 mana if you draw it in the early game. It grabs
Horizon Chimera,
Lathiel, the Bounteous Dawn, or
Accomplished Alchemist for 5 mana if you draw it later.
Overrun,
Overwhelming Stampede, and
Craterhoof Behemoth are classic finishers for green, but might not be what you are going for here.
LOL I just realized you said great staples, not green staples
Heliod, Sun Crowned seems a good fit for this deck.
Walking Ballista wins with Heliod, but also is strong synergy with Lathiel and the
Archangel.
Generous Gift is a white version of
Beast Within and very strong.