So I think I understand how to trim but it never really stated why I should need to trim. Is it just to align my gears?
Yep. Modern systems allow the rider to just "click" a lever and the derailleur moves exactly onto each gear (index). Older systems the rider has to learn how far to move the levers to get to each gear. Trimming on the rear is done to get your derailleur/chain aligned on the cog perfectly (without excessive noise). Trimming the front derailleur is done when the chain has to run at a fairly decent angle (like using the smallest front chainring and some of the smallest cogs on the back) so that the front derailleur won't rub on the chain. You move the front derailleur a little, but not too much or you will actually shift it on accident. If you don't trim the front and just let the chain rub on it, it will tear up the derailleur eventually and will keep it from shifting well.
Hopefully this makes sense.
For chain oil, you can use just about any bike-specific stuff and be ok. I like TriFlow quite a bit myself, but lately I have been making my own chain lube from a 60/40 mix of mineral spirits (paint thinner) and chainsaw bar/chain oil. It works just the same.
Oh, and after you oil you chain - let it dry for a while, then be sure to wipe it down with a rag before you go ride. If you leave it sloppy-wet you'll have tons of crap on your chain after a ride.