Without adding too much more, I am a newbie and a bit along your road.
Focusrite stuff is immense, I have one of the Scarlett’s (your choice number of channels expense etc.)
I would also use garage band (I have done) as it’s a very simple interface, benefit being you already have a Mac, and if you want to increase complexity later on th natural progression would be Logic X Pro, which is like garage band on steroids, very easy to use, and easy to share tracks.
Vicals, whilst probably not being the best I just used my Sennheiser e935 which I would use live (you can use your shure’s) and that will be fine, I ran it through filters or I even used my Cali76G compressor for my bass to decent effect.
Best thing is to enjoy it, and say good bye to hours on end of fun