On a Hobie 14 or 16, you would need 30 feet of 5/16" or 3/8" no (or low) stretch nylon line. That length works just fine on boat boats, but you could probably go with 28' on a 14. You will also need a bungee line about 5 feet long for a 14 and 6 feet long for a 16. Last, you will need 4 3/8" small blocks (like the jib blocks on a 16).
Attach a pulley to the center grommet of the rear lacing strip on the tramp. Either tie a pulley to the front corner casting of the frame, or rivet it to the inside of the casting with an eyelet to hold it. I prefer to mount the eyelet vertically to get the pulley positioned the right way. Tie a pulley to one end of the bungee, pass the bungee through the pulley that is attached to the tramp and then tie the other end of the bungee to the dolphin striker. If you don't have a dolphin striker on a 14, rivet an eyelet to the front frame under the mast step.
To run the righting line, tie it to the rudder pin on one side, run it outside the rear pylon, to the pulley on the front frame, back to the pulley on the bungee (which should be at the rear frame, to the pulley on the other front casting, back around the outside of the other rear casting and tie it off at the other rudder pin. You should use a bowline knot to tie the lines to the rudder pins and have about a 2 foot loop. You can adjust the length of the line by moving the knot.
If you don't want to tie it to the rudder pin, I have seen people drill holes in the lip of the deck that hangs over the transom and tie the line off there. I have also seen eyelets riveted to the lip of the deck over the transom where the line was tied off, too.