Where are you? It always helps to have a location so we know what may do well in your area. Off the top of my head though--if you are anywhere in the eastern half of the USA or Canada, I'd suggest Eastern red cedar--actually a juniper (Juniperus virginiana). This map
https://plants.usda.gov/core/profile?symbol=JUVI shows where it grows natively, so there is a good chance you may already have it where you live. It grows very fast and can be kept pruned to stay as short as you like. It is evergreen, very bushy and prickly, so it makes an excellent privacy fence (can't see through it and don't want to push through it!) It also makes excellent cover for many nesting birds and the berries are eaten by a lot of birds (like Cedar Waxwings) and small mammals, as well as humans--it is used to flavor wild game and in certain alcoholic beverages. It is certainly easy to come by as well. Around here we cut them down as invasive weeds, so I'm sure if you are in cedar country, you can dig up a few small ones just about anywhere. If not, contact your state conservation department and see if they sell them for use in wildlife plantings and windbreaks. Here in Missouri, we can buy them in bundles of 25 for about $4 from the MO Dept. of Conservation.