Forget about using a tuner or some wimpy little loading coil like the ones used on HF mobile antennas. I've seen published suggestions for LowFER loading coil designs that are totally out of the ballpark in Q, inductance or both. Your best bet is to design your own. Litz wire is great if you can find it in large enough sizes. Avoid lossy coil form materials like PVC and Nylon if you want high-Q coils.
Air is the best insulator, but styrofoam comes close.
Other suitable materials are Teflon, polyethylene and polystyrene. Included in Reg Edwards' excellent collection of free software on his G4FGQ web site are programs to design transmitting and receiving loops, coils and vertical antennas. In Reg's programs, wire diameters and coil dimensions are given in millimeters. I've written a program called AWG-COIL that will convert AWG wire gauges to millimeters, and will also calculate the dimensions of a loading coil if you input the desired inductance, wire size and winding pitch.