I didn't know about gel filled ethernet cable existed. 1000' spool is $200, not bad. I better learn how to use a crimper!
I would look at TrueCable. Free shipping. I have bought close to a mile of CAT6 from them.
You want to check the wire gauge and make sure it's copper not copper clad aluminum.
With respect to crimping I am a fan of passthrough connectors. TrueCable sells a crimper as does Platinum Tools.
You want as little untwisted wire as possible. Difficult with regular connectors. With a passthrough connector you smooth out the wires, get them in the proper order and push a passthrough connector onto the cable as far as it will go.
You also need a little tool to strip the outside of the cable. Klein sell a nice one. Yellow with a hole for the cable and round cutting wheel.
The blue untwister/smoother in the screenshot will also be useful. You will realize why after trying to smooth out the wires between thumb and finger a few times.
While a regular wife cutter is handy for some uses the wire snipper is useful for trimming as you are prepping the cable for crimping.
You can get a Klein cable tester for $50 to $75. They test all the wires are connected in proper order.
I test all cabling I work on with a Fluke cable analyzer. It drives a signal through the cable and determines at what speeds the cable will run at and meet specs.