I agree with @Bogleg. That is the best cheap way to start. It’s also the smartest way too. If you like it you can add to it, if you don’t you are not out very much.
It’s a great system. You can expand it easily. You can add an extra bucket and small pump and turn it into a recycling DWC system - PVC pipe and connectors and through-bucket bulkhead fittings are all you need.
I can tell you from past experience, that five gallon buckets SUCK. You have to change them weekly, your pH swings bad, etc. I use 27gal totes. 6 plants to a tote with a 27gal tote for the reservoir. You need to to keep your water @68° or below. I use water chillers in my flower room, and I keep my veg room @66°