If you stop by Starbucks or any other coffee selling place, they will usually give you used coffee grounds by the bucket (you may have to bring your own bucket). When I was working, my office made coffee every day. I brought in a bucket with a tight lid for people to dump coffee grounds in to. Took it home on Fri and brought it back clean on Monday. Despite the color, used coffee grounds are an excellent "green" for the compost pile.
If you are pulling weeds yet, all the pulled weeds can go in the compost pile. An ideal green is manure. Manure for composting can come from bats, sheep, ducks, pigs, goats, cows, pigeons, and any other vegetarian animal. Anyone you know have a hamster or guinea pig? Their used bedding is a good green/brown mixture, having pee and poop added. Or check with local stables for composted horse manure.
Any ponds near by you have access to? Where I used to live there was a big pond at the bottom of our hill. It would get covered in duckweed. I would take a net and scoop the duckweed out and take it to the compost pile. It is very rich in Nitrogen and would heat my pile up like crazy.
Talk to restaurants, groceries, farmers' markets. They may give you some of their scraps or allow you to dumpster dive for them.
You can buy in pet stores timothy hay and/or alfalfa, which they sell as guinea pig feed/bedding. Soak some of that in water to culture appropriate microbes and then dump the whole thing on your pile. (Hay is a green, straw is a brown).
You can buy nitrogen rich additives like blood meal to jump start the composting.