Well your in luck because Druid is within the top 5 strongest classes.
Oddly enough it seems there has been a few "help my druid" threads lately. Just look around and take notes from those as well. Also definitely give the handbooks a look through.
Level 1?
What Race? What Feats do you have selected already? What animal companion?
Since you are already in play, that info would be nice to have before we can get to far into it. Really the best thing you can do as a Druid is know your capabilities. Druids strongest asset is that it usually has an answer to any situation. I would stray away from focusing on any one path of the Druid to much. Meaning like don't go just a summoner, or focus solely on your animal companion.
I would stay with just straight Druid 20. This is my favorite class, I've played a lot of variant builds with it and straight Druid works the best. Trust me just resist the inner min/max urge to take dips or PRC's.
Feats you want IMO: Greenbound Summoning, Natural Spell, Ocular Spell. What ever else you want.
Go download and
print out the Greenbound Summoning list. That way you have everything on hand and you won't need to flip through books to decide which summon is best for the moment.
Now to me it sounds like you want to be a killer. So these are the spells I would keep on hand
SPELLS
0: Detect magic, light, resistance, cure minor wounds, guidance,
know direction, create water.
1st: Cure light wounds, pass without trace, produce flame,
faerie fire, entangle, obscuring mist, speak with animals,
summon natures ally 1.
2nd: Flame blade, heat metal, resist energy, lesser restoration,
bull’s strength, barkskin, summon natures ally 2.
3rd: Cure moderate wounds, protection from energy, call lightning,
meld into stone, plant growth, stone shape, greater magic fang,
summon natures ally 3.
4th: Cure serious wounds, flame strike, dispel magic, command
plants, scrying, freedom of movement, giant vermin, summon
natures ally 4.
5th: Cure critical wounds, stoneskin, baleful polymorph, wall
of fire, call lightning storm, commune with nature, death ward,
tree stride, summon natures ally 5.
Play style Low levels - sit back and let summons/animal companion do most of the work.
Mid levels - Same as above, except now you can start to throw damaging spells in as well. Also Wildshape comes into play now. Fly around as a bird and launch summons into the battlefield .
High levels - K at this point your going to be the main force on the battlefield. charge right into melee as a brown bear or something. take a bad ass animal companion, and launch summons from your eyes via Ocular Spell.
Hope this helps.