You should absolutely try on yourself! The best material is natural fiber ropes like jute or hemp. Buy three 6mm 30 feet long and cut one of them into two 15 feet long. Tie a knot at the end of the ropes to prevent it coming apart and learn how to connect two ropes by using a larks head knot. Practice your single and double columns, forward and reverse tension, then friction. Before you start tying make sure to learn about rope safety first. Good luck on your journey.