Really the tools you would need bare minimum would be a miter saw, you can go hand saw it will just take time. Going handsaw you would need a miter jig. That is how I started out. Now I have a compound miter saw. Some people say that you need a table saw but that is not true. To get the rabbet you can use a router, or you can make the rabbet with a hand saw. Once again going handsawn will take time and precision. A simple router and rabbeting bit will take a few minutes to complete. You can nail the corners together or if you do not want to have mechanical fasteners shown you can use a biscuit cutter and biscuits for the corners. Buying moulding is cheap, and a 8-10' section you can make many frames. If you are not into woodworking, buy a 2x4 and practice on it before trying moulding. You can buy a 2x4x8 for $1.32, that way you can prefect your miters.

Below is a photo of a coffee table I made for my wife from nothing but a picture on the back of a magazine.

Remember to measure twice and cut once. Three sides are easy it's that fourth one that is a killer. 45 degree angles sound easy but be off .05 of a degee will cause you problems when fitting.
Let the prfessionals make your frames and you do the photographic work.

Not to mention space. The tools and wood take space that the OP may or may not have. Then there is the finish work and drying space prior to assembly of the final product.

It can be rewarding, but its a whole nother hobby. Before you know it you could be making frames for every photog around you with no time to shoot.