If you wish to learn from the experience of many beginners, Tommy, I'd say that many of us...maybe most....have changed mouthpieces too soon or too often, in search of a sound which really only comes from practice and more practice, plus listening to lots of the sort of players you aspire to sound like.
Get the sound firmly in your mind, practice lots of long tones, scales and arpeggios ... eventually it will start to come, but it WILL be slow. Boring but true!
Trust me, there are no short-cuts which you can buy over the counter. (I've tried!)
If you have a sax & mpc in good playing condition stick with them for a while.... an expensive mpc won't help significantly at this stage....apart from being nicer to look at! And if you lay out lots of ?? on a mpc now, you will probably need to do it again as your chops develop 🙁
FWIW, I found the Vandoren V5 A25 a really good mpc which I could still be using, if I hadn't been so impatient.
A metal mpc will not necessarily give a brighter sound....I sound much the same on my metal Jody Jazz as I do on my Vandoren Jumbo Java, which cost a fraction as much. I am hoping that one day the expensive JJDV will start to sound better!!
I found that I got along with #1.5 - #2 Rico Standard reeds better than with others, at first (and they are usually cheaper!)...I have moved to Jazz Selects now.
A reed which is too hard for your chops will make the low notes hard to blow.
If you have a good ear for pitch, I think chords & arpeggios are a great way of improving your intonation...it certainly helped me a lot.
And read the Beginner's Diary.....practically all of us can relate ro Chris's experiences.
I still rate myself a very poor player after over 2 years of weekly lessons.... but would have been much worse without a patient teacher!
Good luck.