Layering up for the outdoors takes a bit of practise. It all starts with a good quality, fitted men's baselayer that will insulate you properly while wicking away any moisture so that you don't get chilled to the core. Activity baselayers provide the foundation from which to build up your other layers like a shirt, softshell or midlayer fleece, goose down jacket and waterproof coat. How you layer up is down to personal choice and experience and how your body works whilst enjoying your favourite activities. A quality baselayer either in synthetic fabrics like polyester or natural fibers like Merino Wool is a great way to ensure you are insulated from top to toe.
Baselayers are worn next to the skin, under all other layers. They form a sort of second skin, being like underwear and designed to wick moisture away to keep your core dry and warm. Baselayers aren't just for cold weather as they aren't necessarily thermal. They can be worn under t-shirts and just help you manage your temperature depending on your fitness and exertion. They stop the air moving over your moist skin so that you don't get a wind chill.
Baselayers often have odour control built in since you sweat through them. Merino wool is natural wool from a special kind of sheep. It keeps you cool in summer and warm in winter - like magic! It's also naturally odour resistant (Your significant other might have to force you to wash it one day). If you're walking and camping, go Merino. Polyester baselayers aren't naturally stink free but are very light and often cheaper. Most are treated with an odour control and are very quick drying. Wear synthetic if you are engaging in strenuous activities.