You didn't say what the majority of material on hand is but there's many options for nitrogen depending on what existing material is. I'm an advocate of mulching lawn clippings back onto lawn but catch clippings near hvac to prevent them clogging coils. Weekly addition of clippings from 200 sq ft is more than adiuate for average tumbler. 1 part urine x 5-10 parts water will kick-start it. . It can cause odors but fish scarps are great. Most u-tubes warn against meat but one member here seeks birds, rodents and other wildlife for compost. A shovel of good soil in a tumbler of Fall leaves will produce fine compost. Consensus amongest old timers is "use what you have,it will rot" regardless of n/c ratio.