You don't need trekking poles. You might benefit from them, if steep bits tend to make your knees sore, or if you learn to use them properly. (There are videos online to demonstrate proper use.)

I always use two poles and usually the Gossamer Gear Lightrek 4 poles I got 4-5 years ago. I have never regretted the expense because they have been excellent multi use items, light, durable and well worth it to me to use on steep slopes and crazy stream crossings.

I initially had a pair of Komperdell twist lock poles that failed to lock after about a year. Since I could not find any sort of customer service to get parts or advice, I went to Gossamer Gear and never looked back. The guys at Gossamer answer all my emails the same day, replaced one lower section under warranty, replaced my handles when the marmot ate them, and have earned my faith in cottage gear industry as a whole.

Twist locks are stronger than flip locks (there was an article on this in one of the backpacking magazines) and not all poles are created equal. Folks often start off with Walmart cheap poles that break and bend fairly easily, but, that might be the way to start to see if you actually want to use poles.