I have a tiny desk in my bedroom and what really saved me was using recycled cardboard boxes to store documents and cables - it keeps things organized and costs nothing. Floating shelves are great, but before you go for those, try making use of what you already have at home: an old bookshelf, boxes you got from online orders, even glass jars work for organizing office supplies.
The secret is not to get stuck thinking you need to buy new furniture. A better chair might be worth it (posture matters when you're working from home), but everything else you can make do with. If your desk is too old and cramped, see if anyone in your family is selling a used desk online - it's way cheaper than buying new.