I wouldn't wait much longer, as more producers order their supplies inventories can and do get low. I just ordered from Bascom on Jan 2 (Saturday, ordered online late in the day. Order was shipped Monday. I only ordered 200 3/16 hook connectors, 300 3/16 x 3/16 x 5/16 tees, 100 5/16 hook connectors and 300 5/16 cv2 taps. Everything came, from Bascom to central NY in 2 days transit time.
I normally buy locally, but with Covid I order more online. I still had the rest of what I need, including about 250 drops I made 2 years ago.
If you are going to run tubing for the first time, you need a fitting for starting at the top tree, a hook or other designed for the tubing to go around the tree and connect back to the tubing. Then for each drop, you need a tap, a tee to join to the lateral and a length of tubing. At the downhill end you can run into a collection tank or if you have mainline, you need a hook connector and a saddle. Another method that can be used for both the top tree and at the bottom is some 1/4" hollow braid rope. To use that tie the rope around the tree, leaving a medium long tail. Then take a ball point pen apart and slide the point end onto the tubing and by pushing only force it up inside the center of the hollow rope. Once in 6-8" poke out thru the side and you have an adjustable Chinese finger to hold the tubing. I use 5/16 taps and drops on every tree, the tees are then 5/16 or 3/16 x 3/16 x 5/16 to connect the drop to which ever size the lateral is. The lateral is the tubing going from tree to tree.
csk91, I'm not sure any of us gave an answer to your original question, "the advantage of gravity". Gravity never breaks, it runs for free 24/7/365. Those are two more important advantages IMHO.