Here to help any way I can with hardline.
What size? 12mm 16mm?
What material PETG, Acrylic, metal?
HIGHLY recommend these fittings from Bykski. They are well made, but most importantly have a HUGE O-ring. This is important because it is very forgiving with tension. I think it can handle 10KG of pressure.
https://www.performance-pcs.com/water-cooling/fittings-connectors/bykski-anti-off-rigid-16mm-od-fitting-gray-b-fthtj-l16-gry-b-fthtj-l16-gry.html
1. Recommend PETG to start, it is the easiest in my experience to learn on (Acrylic requires a saw to cut). Make sure you get PLENTY of extra tubing. If your build requires 3000MM, get 6000-9000MM of tubing (Especially for your first build). Recommend this tubing by BP
https://www.performance-pcs.com/water-cooling/water-tubing-soft-hard/rigid-hard-tubing/bitspower-none-chamfer-petg-16mm-od-tube-length-1000mm-bp-ncplt16-l1000.html
2. This bending kit is the one I use, it's well made and a great kit, they make a 12mm variant. Comes with everything you need: silicone insert, deburr tool, tube cutter and mandrels of all angles.
https://www.amazon.com/Thermaltake-Pacific-Cooling-Bending-CL-W093-AL00BL/dp/B01BX3EZUI
3. Will need a heat gun, any old one will do, ones that can stand on their own are beneficial.
https://www.amazon.com/BLACK-DECKER-HG1300-Dual-Temperature/dp/B004NDX7O6/ref=sr_1_8?dchild=1&keywords=heat+gun&qid=1615540929&refinements=p_72%3A1248909011&rnid=1248907011&s=hi&sr=1-8
4. Need thin heat resistant gloves. Don't really need to be heat resistant, but you will need gloves, I promise.
https://www.amazon.com/DEX-FIT-Nitrile-Comfort-Washable/dp/B074X3DPW5/ref=sr_1_14?crid=A17JW80SNWAI&dchild=1&keywords=heat%2Bresistant%2Bgloves&qid=1615540986&s=hi&sprefix=heat%2Bresi%2Ctools%2C164&sr=1-14&th=1
5. Fast tube cutter, though should only use this for splitting long tubes or after a LONG time when you become experienced.
https://www.amazon.com/RIDGID-23488-PC-1250-Single-Plastic/dp/B0019MLSLS/ref=sr_1_13?dchild=1&keywords=tube+cutter&qid=1615540608&sr=8-13
6. Unscented soap. for coating the silicone insert.
https://www.amazon.com/Better-Life-Natural-Unscented-2424L/dp/B01GPWPJTS/ref=sr_1_5?dchild=1&keywords=non+scented+soap&qid=1615541112&sr=8-5
7. Tape ruler. I have gotten to the point that I eyeball measure everything, you may not feel comfortable wasting that much tubing, but it works for me. Very rare that I make a measurement. ALWAYS cut and bend your longest run first, that way if you mess it up, you can use it for a shorter run.
https://www.amazon.com/Measure-Measuring-Measurements-Retractable-60-inch/dp/B07SXFFLMQ/ref=sr_1_2_sspa?dchild=1&keywords=tape+ruler&qid=1615541181&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyQjhYRTJJNjZMN0RWJmVuY3J5cHRlZElkPUEwNTQ1NDQwM0FMTlRVT0hCUzNPWiZlbmNyeXB0ZWRBZElkPUEwNzc0NTk0MVBTQ0sxMlVNSE9VOSZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
8. Make sure you have plenty of 90 degree rotaries to help line up runs that aren't 100% straight, you WILL need a few. Also, a few 45 degree and hard 90s.
https://www.performance-pcs.com/water-cooling/fittings-connectors/bitspower-g-1-4-matte-black-dual-rotary-90-degree-ig-1-4-adapter-bp-mb90r2.html
https://www.performance-pcs.com/water-cooling/fittings-connectors/bitspower-g-1-4-matte-black-rotary-90-degree-ig-1-4-adapter-bp-mb90r.html
https://www.performance-pcs.com/water-cooling/fittings-connectors/bitspower-g-1-4-rotary-45-degree-ig-1-4-adapter-black-matte-finish-bp-mb45r.html
9. Leak Tester. Hardline is not as forgiving as soft tubing. If there is an issue with your run, you will know immediately when you pressurize. I use the leak tester by EK. and I use a bike pump to not have to masturbate the tiny pump 500 times. 2 pumps on the bike pump and it's pressurized.
https://www.performance-pcs.com/water-cooling/accessories-misc/ek-leak-tester-ek-leak-tester.html
https://www.amazon.com/TOOLITIN-Bicycle-Pressure-Compatible-Schrader/dp/B087TCWCPX/ref=sr_1_6?dchild=1&keywords=bike+pump&qid=1615542165&sr=8-6
Once you get everything decided, let me know, I'll make some youtube videos for you to start. Hardline can seem very intimidating to start, but is VERY easy with enough practice and if you stick to simple 90 degree bends for your first run. Multiple bends gets more complicated.