Sister clips vs knots: this is a matter of convenience, and speed, particularly if you are racing in conditions where you don't know which side you will launch the spinnaker on, until you are on the water. If you need to change the side, you need to disconnect the sheets from the sail, then connect them to each other, pull them to the correct side and re-attach to the sail.
With sister clips, one half of each clip is tied to the sail and the sheet respectively. To disconnect, you separate the two halves with a quick twisting motion. You then can connect the "free" halves to connect the two sheets for the maneuver described earlier.
You can do the same with knots, but you will untie and tie a total of 4 bowline's... When I first tried out my spinnaker, I didn't have clips for the lines, although they were on the sail. I just went with the knots and haven't felt the need to upgrade. Not ruling it out, but it's not come to the top of the list so far. (For our races we rarely have true downwind courses, more often it's a broad reach, so it's generally possible to set up the spinnaker ahead of time.)
For the head of the sail you need a swivel, so the sail can untwist. I simply tie on the halyard, using two half hitches or a buntline hitch. Both of these knots tighten under load. The former is easier to tie, the latter more secure. For the sheets, I tie bowlines with a generous loop because I attach the pole claw to it -- mine pole otherwise has a tendency to slide away from the clew along the sheet.
The lines I use are
described here. Those should work for you, except that your bungee needs to be stronger if it's a downhaul. (If you don't know how strong, perhaps get shock cord of sufficient length and double, triple and quadruple it until it works for you.)
The length of the sheets needs to be at least twice the boat size, as, before the launch, one of the sheets needs to go from where you store the sail, to the bow, around the forestay, around the shroud, all the way to the block in the back and then forward to where you cleat it off.