This is what I use:

Base layer--some kind of synthetic wicking layer--no cotton! For inexpensive options see places like Target, KMart, Wallyworld, discount sporting goods stores in the athletic (not sporting goods or camping) clothing department. You should be able to find tall sizes. The idea of the base layer is to wick away sweat, so it should be thin.

Shirt--can either be your baselayer top or a synthetic shirt, maybe supplex nylon. Some people like oversize silk shirts from a thrift store. Again, no cotton. Pants--any synthetic fabric will do. Some like the convertibles whose legs zip off to turn the pants into shorts. Nylon supplex or similar fabric is good. Cheaper version would be nylon track pants from Target, KMart, Wallyworld, etc.

For temps such as you describe (50's sounds downright hot--we have snow forecast in the Cascades starting tomorrow and lasting at least through next weekend), two thin layers are far better than one thick one (such as the REI MTS shirt you link to). That MTS shirt will definitely be too warm to wear while hiking with temps that high. I have a women's version and it's just right for hiking with temps in the 30's. If you sweat up a lather you will then have a wet shirt. When you stop, the wet shirt will chill you. It's better to regulate your body temperature using what I call the "onion" principle--remove layers as you exercise and add them back when you stop. This gets even more important the colder the weather--you want to avoid sweating as much as possible.

Insulating layer--I like a "puffy" synthetic insulated jacket (lighter but pricier), but fleece can be picked up cheap at a thrift store. As long as you can't see through it when holding it up to the light, there's no reason to spend the big $$$ for the fancy fleece at REI. For winter hiking you probably want two insulating layers, one of which might be a vest. Again, I'd rather have two thinner layers than one heavier one, allowing for better regulation of body temperature.

Outer layer--your waterproof layer, such as rain jacket, poncho, etc. Most people prefer waterproof and breathable. If the jacket is breathable enough it can double as a wind shirt.

Also remember the saying, "If your feet are cold, put on a hat." It's true--your head contains a lot of blood vessels right next to the skin, and you can lose a surprising amount of body heat there.

Maintaining proper body temperature--not too hot, not too cold--is vital when you're engaged in outdoor activities. It becomes even more critical when you're out hiking away from "civilization" and your body is your only heat source.