Kornut has a great list there
Sockets, wrenches, pliers, screwdrivers, and a toolbox to keep them in are the most important things you need. That'll cover about 95% of the work you'll do on a car and the other specialized stuff you can rent or borrow. I like having a moderate sized 3 or 4 drawer box that can still be picked up and thrown in the trunk if you need to take your tools on the road. I keep all my basic, core tools in that and then I have a bigger box that other, bulkier and/or less frequently needed stuff goes in.
Craftsman tools are as good as you need for a home mechanic, or even a pro getting started - there is no need to spend the money for Snap-On or the like, save that money for more tools and more parts for you car. I've got a set of Craftsman tools I bought 15 years ago when I worked at U-Haul repairing trailers and I've lost a few over the years but I haven't broken any, unlike some of the cheaper stuff that's found its way into the toolbox in the years since. My 15 year old Craftsman ratchets and adjustable wrenches are still tighter and work smoother than cheap stuff that's only a few years old. The stuff they sell at Lowes & Home Depot looks like it's pretty decent too though, but it's hard to go wrong with Craftsman.
Do avoid cheap, cast wrenches like the plague though - they will break and they are dangerous when they do - quality, forged wrenches only! Cheap ratchets will fall apart after a while, and sockets will split and pliers will get loose and fall apart but you can get away with them if you don't mind replacing them every so often.
Just about everything on the Mustang is metric so get those first before you worry about SAE sockets & wrenches. You need to cover from 7mm-19mm for engine work and you may need a couple of bigger sizes for suspension work. so decent set of 3/8" drive metric sockets should cover most of what you need, but you may need to supplement it with a few 1/4" drive sockets on the small end and you'll probably want some beefier 1/2" drive sockets on the big end to fill out your set. You'll want an assortment of extensions and elbow joints too for those awkward to reach bolts.
It's been a while since I've done brakes - are the caliper bolts star or allen cap bolts, or are they just regular bolts? You may want to pick up a set of star or allen socket bits for that.