"Animist" is the no-subclass option. It gets bonus spells like other subclasses, but has no special class features.
If you like shapeshifting, Shifter is stupid-good. You can't cast spells while shifted, but it's a pretty minor drawback for the sheer boost in power you get (and the free healing). Shifter boar form is insanely good because it's bugged where the damage-over-time effect it has lasts a really long time compared to other druids' spiritshift.
Do you play Path of the Damned? If so, I highly recommend Hold Beasts and/or Charm Beasts, will make the digsite fight waaaaay easier. (don't pick it as your character creation spell so you can respec out of it later if you don't need it... though they are still handy against some dangerous beasts)
I second Sunbeam. Super-solid all-around performer. Damage is low, but the Penetration is high (very useful on path of the damned), and blind is really really a good debuff. It ain't hard CC so it might seem less obviously powerful compared to other tier3 afflictions, but it so terribly punishes recovery, accuracy, deflection (on top of the normal reflex defense debuff) that it is a huge survivability buff.
other spells i like tier 1-3:
the moons's light (solid heal over time spell)
firebrand (couple with ring of focused flame from the dark cupboard [steal or buy]) to be a powerful melee-er
woodskin - basically instant cast, if you cast it from stealth it's basically instant cast and instant recovery. bonus piercing armor can be a life saver (basically makes you harder to punish with ranged damage), and burn and shock are pretty common enemy damage types esp early on (especially early drakes). as a bonus, it's a plant effect that activates the +2 PL bonus for lord of the forest upgrade on lance of the midwood
spreading plague - i'm very bullish on this. lasts a super long time, bounces a lot (if slowly), and making the entire enemy battlefield hobbled and weakened is very effective, both in terms of making it easier for your various spells to land, but also making it easier for your squishies to escape danger and to make life a nightmare for enemy healers
for doing damage, do not sleep on Touch of Rot and Autumn's Decay. They do insane damage, just over time. But compared to other classes, pound for pound you get way more damage efficiency from these little guys. Unlike same-rank Insect Swarm, Autumn's Decay does instantaneous damage as well, has a huge area, and casts faster; it also targets reflex instead of fort, which tends to be a lot easier for the typical druid-inclusive party to debuff, especially early on (on PotD fortitude is a really tough enemy defense in the early-mid game). Insect Swarm is still a good spell, too, just that I think Autumn's Decay might get slept because no subclass gets it for free, and it doesn't do raw damage or remove concentration.