WPK. If you have a floating windcutter you can do what I did. Simply measure back 15 feet from the tip, cut it and put in your own loops. many guys make their own loops but I have had no problems with just the regular cortland braided loops with shrink tubing. Put them on as the instructions say then super glue both ends of the shrink tubing.. I am sure there are better ways but I like things that are simple.
The length of sink tips you should make depend on where you fish. I'd recomment starting off with buying a 30 ft type 6 shooting head and making a 12 ft tip and an 18 ft tip. If you can afford more do the same with a 30ft type 3 shooting head. If you don't want to do that I recommend buying the premade tips from Rio.
An inexpensive way to go is to buy some LC13 (lead core)and just make a bunch of different lengths of tips with that. I suggest 12, 15 and 18 ft lengths of that..
It will also somewhat depend on what your rod will handle. Longer rods typically handle tips better.