L-Arginine will make the pump feel better and help with blood flow, but you can pump without it. It makes it more fun, but personally, my eye starts to twitch if I use L-Arginine a few days in a row.
Pumping should be long term, with breaks often. 20 minutes at a time max, massage or jelq, and then pump again. using a heat pad before pumping or any type of PE is important as well.
But you say you really hate the gym? Then you are limiting yourself significantly. The heart powers the dick. It doesn't have to be the gym, but run, do yoga, whatever. The healthier you are, the easier any type of body sculpting (including PE) Will be. No supplement or device will ever replace a healthy diet and exercise for making your dick harder, work better, and gain better. Not only for your dick, but over all health and wellness and even emotionally. I use to suffer from depression constantly until I started exercising consistently. I'm not saying exercise will cure depression, but lack of exercise can cause depression.