“Essential” is one of those great words, it really depends on what you are planning. The true essentials; shelter, bedding, enough food and water are obvious. A PLB, water filter, first aid and survival kit with snake bite bandage I personally add to that category as well. The rest depends on your hike;
Where are you planning to go? Depending on the terrain you may need proper hiking shoes or boots for protection, if you’re only trekking on well maintained tracks you could use trail runners and save some weight. With steep inclines hiking poles are great & can really save strain on your legs. With the weather warming I really recommend knee high gaiters in case of snakes
What is the expected weather? Will you need rain gear or a good sun hat and buff or both. If the nights are going to be cold fleece pants and top or down jacket can be the difference between being comfortable or freezing cold.
Is there a water source or do you need to carry all of your water? One of my personal favourites; carry too much water and you get weighed down, don’t carry enough and you can end up in real trouble. I carry 3 litres per day as a minimum, more if water sources are sketchy or unreliable. Make sure you know where the water sources are along your route, plan to overnight at a water source if possible, have a plan B just in case and know where properties or dwellings are located near your route
A bit of a long-winded reply and I am by no means an expert overnighter having only done a handful myself but outside of the “true essentials” the rest will become apparent when you do your planning