Welcome to deer hunting. You are already off to a great start. You live on 20 wooded acres that has a deer population with food, cover and possibly even bedding areas. You don't need to feed them (illegal in most states) and they obviously have some source of water. Now you just have to figure out how to hunt it successfully.
Read through all of the above advice and consider what would work for you on your property. Since you don't want to spend any money, you'll have to develop your hunting methods accordingly. If you haven't already, learn your property and the surrounding areas (neighbors' property). Figure out where you can shoot safely and where you can't. Are the deer bedding on your property or a neighbor's? They obviously can get food on your property but do they also get food on the neighbors' properties? Water? Bedding? Do they neighbors have houses, barn, sheds or other buildings on your shared property lines? Are there any trails between your property and the adjoining neighbors property? Is the neighbors property also brushy with acorns or do they have more clearings, etc.? Learning more about the terrain on your property and the neighbors will allow you to figure out better locations to hang a tree-stand or even set up a ground blind.
If you do end up building a tree-stand, you are shooting at a downward angle that is less likely to have a slug travel onto a neighbor's property. If you search this website, Hardcastonly wrote some very informative topics about beginning deer hunting, specifically in brushy areas with a tree-stand. His topics were about hunting thick brush in Florida but could obviously have some application on your property.
You mentioned a clearing where you saw deer "once." That's a good start. Do you have trails or shooting lanes you can observe? Will your parents let you clear some brush if needed? Will they let you build wooden tree-stands that are attached to the trees? You said it's hard to walk around without making a lot of noise due to acorns, etc. If you're sitting in a tree-stand and not fidgeting or making noise, you have a better chance of seeing deer in clearings, shooting lanes, etc. Since you live on the property, that gives you a lot of opportunity to simply find different vantage points and observe the deer. The best times are early morning and in the evening around dusk. If you own a pair of binoculars, use them to slowly scan through as much of the property as you can see from different vantage points. If you don't already own a pair of binoculars and still don't want to spend a lot of money, consider looking at a thrift store for an older pair. A buddy of mine bought an old porro prism pair of binos at a thrift store for $5. They are going to compete with binos costing lots more $ but they worked and you could see a lot more through the brush, etc. with them than without. Look for maybe a 7x or 8x set with at least 40-50mm objective and you should get some use out of them.
If you can, just sit out in your yard where you can see a lot of the property during the evening and watch patiently. I once turned an old and rotting piece of plywood on its side at a buddy's ranch and sat behind it in a chair so it blocked a lot of my movements from sight of the critters. A coyote showed up about 80 yards from me by a wild fig tree and stood staring at his kenneled dogs. That was a fun shot. I don't know that I would get a similar shot opportunity again but it was fun and, as always, I learned from it.
Now down the road, if you decide to spend a little money, consider getting a game camera or 2 so that you can get an idea of what deer show up on your property, where and when. Instead of building a wooden tree-stand attached to a tree, consider buying either a climbing tree-stand or even a ladder tree-stand (both can be moved around). A fair warning though. If you find most of the deer come out in the evening just after dusk, it can get a little expensive trying to buy binoculars that see better in low light. You don't have to spend money to deer hunt but most of us end up spending a lot of money, often just trying something out to see how well it does work or if it works better than what we already have. Enjoy the hunting and the learning curve.