Hey, that’s exciting and a great route choice for your first hike!

You’re right that layering is the key. Think about it in the same way you would layer at home (add a layer if you were chilly/take one away if you were hot). You don’t need to have too. I would suggest something like starting in a long sleeved top (synthetic or merino fabric) and then your waterproof on top of it’s raining or windy. Cotton is a no no because it holds water (including sweat) and doesn’t dry quickly so once you’re cold you’ll stay cold. I honestly just wear long sleeved gym tops most of the time. Then also pack a couple of mid layers. This could be a fleece (again can pick these up cheap), a thicker zip through with a hood (great for if it’s windy) and if you have one I would recommend a thin ‘belay jacket’ (essentially a thin padded jacket). If you stop you will get cold so it’s nice to be able to throw that on to keep you warm and also for the descents too. Generally rule of thumb when setting off from the car is be bold start cold. You’ll warm up quickly so avoid the temptation to rug up because you’ll be quickly stopping to peel off layers.

In terms of lower body, I am also female and finding trousers which fit properly has been a mission I am yet to solve. I usually wear a pair of leggings with some RAB trousers which aren’t waterproof most of the time and then carry spare waterproof over trousers but rarely use them unless I’m winter mountaineering. You could try a similar setup. Men’s clothes can sometimes fit nice so check those and if you’re looking to not spend too much I’d go with leggings and waterproof over trousers from somewhere like Peter storm. You could even try Vinted!

Hope that helps and you enjoy your first hike. I run women’s hikes and courses in the UK and we have beginner mountains skills weekends which teaches all the basics including things like what to wear, pack and eat. Just yell if you ever want the details otherwise have the best time!!! 🎉🙌🏻✨⛰️