Should I specialize in multiple elements or one?

I'm new to the game and I wanted some advice before I got too far with my build. I was thinking of alternating between lightning and ice and taking advantage of the Elemental Equilibrium passive. Is Elemental Equilibrium at all useful? Should I specialize in a different combination of elements? All three? Just one?
I'm also wondering about other game changing nodes like Chaos Inoculation. It seems bogus at first glance, but I'm still at the beginning of the game. If I get it I'll at least know to avoid life and chaos resist passives. Does the Zealot's Oath passive benefit from life regen passives as well as life regen equipment?
What other passives should I stack: spell damage, elemental damage, cast speed, mana regen, energy shield, etc.?

If this is your first character I'd focus on just 1 element, and go life based.
Chaos Inoculation is very handy, but it makes your gear need to be more specialised in order to gain the required amounts of energy shield.

Elemental Equilibrium can be handy, say if you have a Fire based character, and have an ice attack (such as ice Spear) linked to a Spell Totem with Faster casting, so that your fireballs will deal more damage.

You'll generally want to focus on life, resists, cast speed, spell damage and armour/energy shield

Chaos Inoculation is actually pretty good. For a single point, you get instant, permanent immunity to Chaos damage, which is one of the harder damage types to get resistances for, from what I understand. In exchange, your Life is set to 1. This means that your Energy Shield goes from being a second Life Bar to being your only Life Bar. The other advantage is that you don't have to worry about picking up Life nodes in the Passive Skill Tree (since they won't do anything for you), so you can concentrate on other nodes instead.

Thanks for the input, but I think I'll avoid Chaos Inoculation. It just seems too difficult to manage without HP, though I imagine late in the game all the most powerful monsters do chaos damage. My next big question is whether to get the +1 curses passive. I already made some progress towards it, so I would have to undo some skill points if I decided against it. It seemed like a good idea when I was considering using multiple elements (which I still am considering) but it may not be worth all the skill points or the time it takes to cast them both.
Another question I have is about power charges. There doesn't seem to be a good way to accumulate them. The Power Siphon skill doesn't seem very effective and the benefits of the power charges would seem to be negated by the time I spend using the skill. Also, I don't think the 'Power Charge on Critical' works with spells but I could be wrong.

Chaos damage isn't that common, but doubly problematic when it DOES occur. Late game you mostly see it in maps as very few or no boss actually deals chaos damage.

There are several nodes that have +spell damage and +elemental damage, but skill wise it's easier to concentrate on one skill.

Chaos Damage is only a problem for ES-toons that are not CI and have no Shavronne's Wrappings, and for them it is a lethal problem.

All my other chars have -60% Chaos resistance and thrive.