Yeah, I wouldn’t bother with bi-wiring either. You can buy decent speaker cable from Amazon, nothing special, but not terrible either. At around £8 to £15 it will be fine to get your system up and running and you can then look into other cable later on.
As for the TT cable, it depends how DIY capable you are. You could buy a half decent set of cables, take the phono plugs off at one end and then use the lead to rewire your TT. This will require you opening up the TT and performing a bit of surgery. Or you could snip off the din connector and solder on some phono plugs, or just go for an adapter for now.