The best melee fighter companion at level 1 is the riding dog (or the shark...). Check with your DM for his definition of "trained for war," as having this allows riding dogs to have a wolf's trip ability.
Nothing catches my eye at level 4. Leopard is ok...only cause I like pouncing cats...
At level 7, lots of great options. My favorite is Tiger, but Brown Bear and Giant Crocodile are also wonderful. Rhino can be good, especially if a spiritied charge-based ally is riding it with a lance.
For magic items, I don't know of many specifically awesome to druids other than periapt of wisdom, amulet of retributive healing, and wilding clasps. (All but periapt in Magic Item Compendium) MIC also had a collar for animal companions to get extra healing, I recall.
Spells: Just try things out, you know your whole list, can always change things later. Never memorize a SNA spell, you can just do that spontaneously if needed. Frostburn has the Summon Ice Beast line of spells, byond that you can stick with the PHB and Spell Compendium and be pretty set. To me, an "earth focus" means flying over it and smothering the ground in things like spike stones to punish and gimp anyone foolish enough to restrict themselves only to it for movement.
A druid can pull this kind of "earth focus" off rather well...
Some spells from SpC, not going to bother w/ the PHB ones, you should have some idea of what's good there:
1
*Lesser Vigor heals more than CLW, though eventually you'll just want wands of it.
*Crabwalk is a nice boon to charging allies.
*Enrage Animal does...exactly as you'd expect.
2
*Kelpstrand is one of the greatest spells...ever. Note VERY carefully what is replaced by CL and wis mod...you still add BAB, too! Due to slow progression of strand numbers and the nearly "double whammy" of each level up adding 1 3/4 (CL + BAB) to the grapple check, this spell starts weak at level 3 and becomes stronger as you get higher.
*Master Air is a level 2 fly spell, what more should you care?
*Blinding Spittle can be incredibly powerful if the enemy has no means to wash its eyes out (blindness w/o a saving throw)
*Mass Snake's Swiftness gives potentially all alllies an immediate free melee attack.
*Listening Lorecall, with listen ranks, will eventually give blindsense and blindsight for 10 min/CL.
*Blood Frenzy gives someone w/ Rage class feature a free usage.
*Earth Bind prevents a creature from flying, may fit your theme.
3
*Spirit jaws is like a spiritual weapon that can grapple and pin.
*Vigor is just a better deal for you than Cure moderate due to Druid's delayed cure spell acess. Mass Lesser Vigor is also not bad.
*Entangling Staff gives you free action grapples after hitting with your staff, if you're out of wildshape.
*Downdraft knocks flying creatures down, may fit your theme.
*Giant's Wrath lets you hurl boulders!
*Girallon's Blessing gives someone +2 arms, always useful. And for 10 min/CL!
*Mass Energy Resistance is just a great buff to keep prepared.
4
*Enhance Wild shape gives Ex qualities of the form you take!
*Arc of Lightning offers no SR.
5
*Rejuvenation Cocoon is almost as good as heal, at two levels lower.
*Dire Hunger isn't optimal, but it sure is funny.
*Bite of the Weretiger is the lowest level "Bite of the x" spell REALLY worth using. Massive stat bonuses. Also look at all higher level versions.
*Greater Vigor heals enough per round it may even be worth using in combat.
If you really want an earth focus, there's also Foundation of Stone, Mountain Stance, Earthen Grace, Earthfast, Crumble, Nature's Rampart, Land Womb, Lay of the Land, Greater Stone Shape, and Wall of Sand (along with many spells in the PHB) from spell levels 1-5 as well, but they aren't that amazing in general use.
