3. Seaweed would be a "green", but it is a good addition to any compost pile.
2. Twigs and branches can be "browns" the C:N ratio of wood chips ranges from 400 to 800 to 1.
1. Conventional wisdom has it that after 3 or 4 mowings after the application of synthetic fertilizers, weed killers, etc. grass clippings are okay for an organic gardener to use in compost. The nutrients the grass clippings contain are chemicals, but necessary ones. Grass clippings are primarily Nitrogen, although there are others in lesser amounts in them.

Perhaps the link will be of some help.

Here is a link that might be useful: Composting Tutorial

There is a whole forum dedicated to soil, mulch & composting. You may find some of the discussions helpful, if you're interested in checking it out. Getting started is the hardest part for newbies but there's no reason to over-think it.

There's no reason not to start a little open pile until you get ready for your "setup," whatever that might be. Put a banana peel down and put a few leaves on it. You've begun composting. Add whatever kitchen/yard scraps/trimmings you can, when you can (with whatever exceptions you might make for personal reasons.) It will happen from 100% green to 100% brown, and any degree in between. What people discuss are the speed at which this happens and the qualities/inadequacies/results of different combinations and locations/gadgets for doing so. ...differing personal preference, locations, available materials, lifestyles, and many other variables.

You will read about ratios and temperatures, bins and piles, turning and screening, but don't get too lost in stuff that's not what you want to do, or the way you want to do it. The basic principle is that stuff decomposes with or without our help. Gathering it in a pile is what makes it "composting."

The few basics over which you have no control, you'll notice as they repeat themselves over and over. Poison ivy/oak/sumac are not usually composted. Large quantities of just oak leaves can take forever to decompose. Large pieces of wood also take a long time and are usually put in a separate pile by those who have room for such. Weed seeds are not welcome. Stuff like that.

Good explanation purpleinopp & advice to skip the big chunks of wood & the weed seeds.

Most of us compost in a variety of ways....tucking in small piles wherever we can, digging a hole to bury kitchen scraps, worm bins, sheet composting in place, and larger piles as space allows. A compost bin is just one method that works.

A variety of materials, turned regularly for a hot fast pile or left alone as a slow, cold compost method both make usable compost.

I am assuming you want faster made hot compost for use this year in your warm southern CA climate. You can search for info on the soil forum. You don't need a bin for hot compost, but you do need a pile at least 3 feet square. Kept covered with whatever you have will speed things up (old carpet, tarp, tablecloth, even a large piece of cardboard works in a pinch)

With a little bit of hunting around you can find free materials to build a big pile -- sometimes craigslist is a place to find them.
-used coffee grounds & filters from coffee shops (ask ahead & they will more likely save up for you)
-hay sweepings from a feed store (wear a dust mask, gloves, & long sleeves to bag it up yourself - ask the workers 1st & they've always told me yes and have had plenty for me to bag up.
-manure + bedding (ideally from a farmer who also gardens so you can inquire if they use it and how their stuff grows -- to avoid the herbicides used on hay fields that persists in the manure..., whatever type you get should work - horse, chicken, goat, rabbit, alpaca, or llama are ones we've used. Many people like sheep or cow manure as well.)
-scrap office paper, newspaper, cardboard to shred or tear up for faster composting

Household paper collects quickly if you have a separate waste bin for family members to quickly toss instead of using the trash -- used paper napkins, facial tissues, toilet paper rolls, cereal or cracker boxes, junk mail, etc. + vegetable or fruit waste, tea bags, egg shells, leftover plain rice or noodles, dry bread, etc.

If not enough greens & you want to speed up the pile you can mix in cheap dog food which is mostly cornmeal that really gets the pile going. I've tried it 2x using it to keep a huge pile cooking last year, but I probably won't do it again. Too much work to turn & mix it all in thoroughly because I didn't want to attract vermin. One bag was a freebie & the other a discounted torn bag - a manufacturer's coupon purchase, so my cost wasn't much. Manure seems to do the same thing without the vermin risk.

Sometimes, I've worked a pile turning 2x the 1st week then about every 5-6 days after that adding some water as I worked it if too dry. Then after it no longer heated up kept covered to cure. If you want to use it right away it will be a bit chunky depending on the ingredients & you can screen it simply through some wire mesh or a black plastic plant tray. As mulch the chunky works just fine.

Once you make your 1st batch you'll find all sorts of ingredients to compost around the garden & you might gather up enough for all you need. The first few years of a garden you need a lot more compost than after a few years, so don't give up after your 1st batch. I still haul in a few pickup loads of manure + bedding in the fall especially if I'm making a new garden. This year I probably will only use one load because I got a few loads very early this spring as well. I have a few regular contacts nearby & it works out well because their horses produce a lot of manure.

Thank you for the tips everyone!! :D

Dry leaves are easy, if shredded first.
Most anything compost better, if it is shredded first.
I picked up grass clipping in bags & put them in the back yard & forgot about them until about a year later, this June.
I moved them & torn the bags open & found compost with earth worms, one had 10 or 12 E. worms in it.
So compost is easy, even if you do not turn it. The reason the grass clippings composted by them self is they are high in N & are chopped up or shredded.