how realistic is it to buy a block in 2026 as an individual? I understand that it is useless, but how much so

Different RIRs & LIRs have different policies, but the "foolproof" way is to just set up an LLC and register resources through that. There are usually renewal fees as well. If you're not hoping to be able to sell them after you get them, a careful reading of RIR policies can usually net you one or two /24s without needing to buy any blocks.

In either case, if you end up with internet resources you can trawl through sites like https://bgp.services/ to find a cheap VPS provider near you that supports peering. I run my own AS and advertise 3 network blocks (2 IPv4 + 1 IPv6) out of 2 different DCs for several hundred $ per year all in all (including renewal fees, VPS, taxes, etc).